About

About this peril

Flooding is water covering land that is usually dry. It can come from rivers and streams that overtop their banks, intense rain that overwhelms drainage (flash flooding), storm surge and waves on the coast, or blocked or failed drainage systems. Even shallow, slow-moving water can damage foundations, utilities, and contents; fast-moving water in a channel can erode banks and sweep away vehicles.

In the United States, the Special Flood Hazard Area is the 1% annual-chance floodplain—the area FEMA maps as subject to a flood with about a 1-in-100 chance in any given year (often called the “100-year flood”). That label describes probability, not a clock: several such floods can occur in one decade. Zone X includes land outside that floodplain; where FEMA maps it, the 0.2% annual-chance (500-year) floodplain sits in Zone X as well. Levees reduce risk only where they are designed, maintained, and shown on the effective map as providing protection.

Coastal flooding adds tide, surge from tropical cyclones and nor'easters, and wave runup on top of elevated water levels. Riverine flooding depends on upstream rainfall, snowmelt, and channel capacity. Flash flooding depends on how quickly rain runs off impervious surfaces and how soil absorbs water. Height above the nearest stream a property drains to—not just distance to the closest named river—often explains why one lot floods while a neighbor’s does not.

Methodology

Peril Report looks up the FEMA National Flood Hazard Layer for the point that matches your address. The headline is the mapped flood zone, with the annual chance of flooding where FEMA publishes it. Show on Map overlays FEMA flood hazard zones on the address map and places a legend under the map. Street, satellite, and elevation views are available (OpenStreetMap streets, Esri satellite imagery, and USGS 3DEP lidar hillshade with highlighted NHD streams, rivers, and lakes, tinted from red at the lowest point in the original view to green 30 feet above it); a pin marks the looked-up point without an address popup.

When FEMA publishes preliminary flood hazard data for an area, the Flood section states effective and preliminary status together (for example, whether the point is in either map). Preliminary data is for early awareness only and may differ from the effective map; it is not used for flood insurance rating or mandatory purchase until FEMA makes the data effective.

Letters of Map Change are read from the same effective National Flood Hazard Layer. A Letter of Map Amendment (LOMA, including a LOMR-F) is included when its mapped point is within 100 feet of the address. A Letter of Map Revision (LOMR) is included when its mapped area contains the address. The case number, status, and effective date are shown. A letter that FEMA has not drawn onto this layer yet will not appear.

Special Flood Hazard Areas (typically A and V zones) are the 1% annual-chance floodplain. Zone X includes areas outside that floodplain, including the 0.2% annual-chance (500-year) floodplain when FEMA maps it. A levee is noted only when FEMA’s zone subtype says the area is protected by a levee.

If the point is not in a mapped flood zone, the report shows the nearest mapped zone within 2 miles. Nearest flowing water is the closest creek, stream, or river on an NHDPlus flowline from the USGS National Hydrography Dataset, named from the EPA NHDPlus service. The same line says how many feet that closest point sits below the address, from USGS 3DEP ground elevation. The water value is the ground where the mapped line sits, not a flood stage. The 1% flow is the peak streamflow with a 1% annual exceedance probability at that point, from USGS StreamStats. The elevation graphic is the USGS 3DEP ground elevation from the address to 20 meters past that stream, on 1 meter ground near the channel. A satellite view of that same line is shown under it, on the same horizontal scale. Blue shading is the wetted 1% flood cross section at the stream: StreamStats peak flow above mean flow, routed through the 3DEP valley section with Manning's equation to a water surface and cross-sectional area in that vertical slice (not horizontal map area; speed is flow divided by that area).

Height Above Nearest Drainage (HAND) is the vertical distance from the address down to the stream it drains to. In the contiguous U.S. it is read from the National Flood Interoperability Experiment CONUS HAND rasters (Oak Ridge National Laboratory, hosted at the Texas Advanced Computing Center), computed from 10 m USGS 3DEP bare-earth terrain and NHDPlus medium-resolution streams. The cell containing the address is read directly from the HUC6 basin raster. Elsewhere, or if that read fails, it falls back to the Alaska Satellite Facility Global HAND dataset, computed from the 30 m Copernicus GLO-30 surface model, which includes tree canopy and buildings. HAND measures to the stream the address drains to, which can differ from the nearest flowing water.

The Flash Flooding figure is the 1% annual-chance (100-year) 1-hour rainfall intensity from NOAA Atlas 14, queried at the address from the Precipitation Frequency Data Server. Values are partial-duration series estimates in inches per hour. The figure is omitted in regions Atlas 14 does not cover, including much of the Pacific Northwest. The comparison says how much of the contiguous US has a lower value. It uses the area-weighted NOAA Atlas 14 grid of the same 1-hour figure. Alaska, Hawaii, and unpublished areas are left out.

Below it, the hydrologic soil group is the dominant-condition rating for the soil map unit at the address, from the USDA NRCS Soil Survey Geographic Database (SSURGO) through Soil Data Access. Groups A through D rank how quickly soil absorbs water after it is thoroughly wet, from A (sand and gravel, low runoff) to D (clay, high water table, or shallow bedrock, high runoff). Dual groups such as A/D give the drained and natural ratings for soils with a high water table.

About this peril

A tropical cyclone is a warm-core storm with a closed circulation over tropical or subtropical waters. Below 39 mph (34 kt) sustained wind it is a tropical depression; from 39–73 mph (34–63 kt) it is a tropical storm and receives a name. At 74 mph (64 kt) or higher the same storm is called a hurricane in the Atlantic and Northeast Pacific, a typhoon in the Northwest Pacific, and a cyclone in the South Pacific and Indian Ocean. Subtropical cyclones blend tropical and extratropical structure and can still produce damaging wind, rain, and surge.

Property damage comes from several mechanisms at once: wind that peels roofs and pushes water through openings; heavy rain and inland flooding; tornadoes embedded in rainbands; and storm surge—elevated ocean water driven ashore by wind and pressure, often the greatest killer in coastal hurricanes. Surge height depends on storm size, angle of approach, forward speed, coastal shape, and astronomical tide, not on category alone.

Major hurricanes (Category 3 and above on the Saffir–Simpson scale) carry enough wind to destroy well-built homes near the eyewall and can reshape coastlines through surge and waves. Even weaker storms cause widespread power outages and tree damage over large areas because tropical-storm-force winds extend far from the center.

Live outlooks and historical tracks are on the Forecasting page.

Methodology

Hurricane chances on Peril Report come from NOAA IBTrACS (International Best Track Archive for Climate Stewardship). Storms are counted from 1950 onward when the U.S. wind speed reaches hurricane force (64 knots, Category 1) or major-hurricane force (96 knots, Category 3).

A storm counts if its center passed within 50 miles of the geocoded address location. Unique storm IDs are used so one hurricane is not counted twice. The annual chance is a Poisson estimate from that history: 1 − exp(−count / years). The insurance chart rates tropical cyclone risk as None when the Category 1 or above IBTrACS annual chance within 100 miles is below 0.1%, Very Low when the chance within 50 miles is below 0.1%, and otherwise from the county expected annual loss rating. The rating in that section is FEMA’s National Risk Index tropical-cyclone expected annual loss rating for the county, which is separate from the IBTrACS strike chances. The percentile bar is the tropical-cyclone expected annual loss rate compared with other U.S. counties. The text also prorates historic and modeled building-loss ratios over 30 years.

Hurricane storm surge comes from the National Hurricane Center’s National Storm Surge Risk Maps, the same public maps at https://www.nhc.noaa.gov/nationalsurge/. Those maps take SLOSH Maximum of Maximums (MOM) water levels at high tide and convert them to inundation above ground on a ~10 m DEM. Peril Report lists the NHC depth class for each hurricane category (1–5) that inundates the address, labeled as water depth from a worst-case storm of that category. Depths use NHC’s published bins (< 3 ft, 3-6 ft, 6-9 ft, and > 9 ft). A category is omitted where that storm does not flood the location. Leveed areas are shown as such. If the maps show no inundation but historic hurricane chance is at least 0.1%, the same cited box states that the location is not expected to be exposed, based on storm, tide, and elevation modelling. NHC does not cover the Pacific Northwest or Alaska.

For Gulf and East Coast counties that Colorado State University covers, Peril Report also shows that year’s Tropical Cyclone Impact forecast: the probability of a hurricane and of a major hurricane tracking within 50 miles. Those seasonal odds are adjusted from 1880–2020 climatology using CSU’s latest Atlantic forecast. They are omitted when CSU does not publish a forecast for the county.

About this peril

Wildfire is unplanned fire in vegetation. In forest and shrub lands, flames move with wind, slope, and fuel type—grass and fine fuels ignite quickly; heavy timber burns longer and can produce intense heat and embers. Prescribed burns and agricultural burns are managed fires and are a different peril from uncontrolled wildfire, though smoke can still affect nearby communities.

The wildland–urban interface (WUI) is where homes and wildland fuels meet. Most homes lost in large fires are not touched by a wall of flame; they ignite from embers landing on roofs, gutters, decks, and vents, or from neighboring structures that already burn. Defensible space, hardened building materials, and community fuel treatments reduce but do not eliminate that exposure.

Red-flag weather—hot, dry, windy conditions—raises the chance that a spark becomes a fast, large fire. Past fires near an address show that fuels and weather have aligned there before; they do not by themselves predict the next ignition, which may come from lightning, equipment, or power lines miles away.

Methodology

Peril Report searches mapped wildfire perimeters within 20 miles of the address. Historic fires come from the NIFC Interagency Fire Perimeter History layer. Recent fires, including current-year perimeters, come from WFIGS Interagency Fire Perimeters. Prescribed burns are left out.

If the point sits inside a perimeter, the report says the location burned over and, when more than one unique fire is mapped there, how many times. Otherwise it names the closest mapped fire, when it burned, and its size. Beyond 20 miles, it only says the closest mapped wildfire is more than 20 miles away.

Nearby fuel treatments are searched separately, within 2 miles: completed USDA Forest Service FACTS Hazardous Fuel Treatment Reduction polygons (thinning, mastication, pile or broadcast burning, and similar work) and NIFC or WFIGS prescribed-fire perimeters. Those operations can reduce local fuels. They are not mixed into the closest-wildfire sentence and are not the same as the WRC Community Wildfire Risk Reduction Zone.

The rating is FEMA’s National Risk Index wildfire expected annual loss rating for the county. The percentile bar is the wildfire expected annual loss rate compared with other U.S. counties. The text also prorates historic and modeled building-loss ratios over 30 years. Red-flag warning counts from the past 10 years are included when that record is available, on the same line as the closest mapped wildfire.

Risk to Potential Structures comes from the USDA Forest Service Wildfire Risk to Communities 30-meter raster (USFS WRC Risk to Potential Structures). It combines wildfire likelihood and intensity with generalized consequences to a home at that pixel: the relative risk to a house if one existed there. Annual burn probability at the pixel comes from the WRC Burn Probability raster (Wildfire Likelihood) and is shown as the chance that location burns in any given year. Classes are Low, Medium, High, and Very High using national pixel percentiles from the WRC methods (below the 40th, 70th, and 90th percentiles). The Community Wildfire Risk Reduction Zone (USFS WRC CWiRRZ 4-class raster) is the exposure type at that pixel: minimal, indirect (embers and home-to-home), direct (adjacent vegetation plus embers), or wildfire transmission. The underlying spatial datasets are cataloged in the Forest Service Research Data Archive as RDS-2020-0016-2 (https://doi.org/10.2737/RDS-2020-0016-2). The full recommended citation appears at the bottom of each address report.

For California ZIP codes, the report also shows the CAL FIRE Fire Hazard Severity Zone at the point (CAL FIRE OSFM FHSZ maps). State Responsibility Area zones are the adopted April 2024 map. Local Responsibility Area zones use CAL FIRE’s 2025 recommended classes (Moderate, High, Very High). Points outside those polygons are reported as not in a mapped zone.

About this peril

Severe convective storms are thunderstorms that produce hail at least one inch in diameter, wind gusts of 58 mph or more, or a tornado. They build from warm, moist air rising into cooler air aloft; wind shear tilts and rotates the updraft in the storms that cause the worst property loss. Outbreaks can track across several states in a day, hitting many counties with different combinations of hazards.

Insurance and emergency management often treat hail, tornado, and straight-line wind as separate loss drivers, but they share the same storm environment. A single supercell can drop baseball hail on one farm and produce a tornado ten miles down the road. Derechos—long-lived wind storms—flatten trees and peel roof decking over corridors hundreds of miles wide without a tornado.

Read more about hail and tornadoes as distinct perils within this group.

Methodology

Hail and tornado results on Peril Report are described in the Hail and Tornadoes sections below.

About this peril

Hail forms when strong updrafts in a thunderstorm carry raindrops into cold air, where they freeze and collect additional layers of ice before falling. Stones can grow to golf-ball or larger size before gravity overcomes the updraft. The Great Plains and Front Range see the most frequent large hail in the United States, but damaging hail occurs from the Rockies to the Mid-Atlantic and Gulf Coast.

Damage scales with stone size, wind-driven angle, and exposure. Asphalt shingles lose granules and mat integrity; metal dents; skylights and windows break; siding cracks on vinyl and fiber cement. Vehicles left outdoors often show clustered dents on horizontal surfaces. Crops and greenhouses suffer total loss in minutes in the swath under a severe core.

Hail is usually part of a severe convective storm that may also produce tornadoes and straight-line wind. Spotters and radar estimate hail size from reports and reflectivity signatures; the largest stones fall near the strongest updraft, not always where rain is heaviest.

Methodology

Hail on Peril Report uses FEMA’s National Risk Index for the county. The headline is the expected annual loss rating (for example, Relatively Low), not the composite hail risk rating that also folds in social vulnerability and community resilience.

The percentile bar is the expected annual loss rate compared with other U.S. counties. The text also reports how often hail occurs in the NRI record and prorates historic and modeled building-loss ratios over 30 years.

About this peril

A tornado is a violently rotating column of air in contact with the ground, usually extending from a thunderstorm. Most strong tornadoes form under rotating supercell storms in the central and eastern United States, but tornadoes occur in every state. They can be narrow and short lived or long-track wedges more than a mile wide; forward speed adds to wind speed on the leading edge.

Damage is from extreme wind and airborne debris, not from lower air pressure “exploding” a house. Weak construction and large openings (garage doors, windows) fail first; well-anchored roofs and continuous load paths survive longer. Mobile homes and unreinforced masonry are especially vulnerable at EF1 and EF2 intensities.

Tornadoes are often embedded in broader severe thunderstorm outbreaks that also bring large hail and straight-line wind. Nighttime and rain-wrapped tornadoes are harder to see and give less time to shelter in an interior room on the lowest floor, away from windows.

Methodology

Tornado chances use NOAA Storm Prediction Center SVRGIS tornado paths from 1950 through 2024 (the same historical layer as FEMA’s Resilience Analysis and Planning Tool). Peril Report counts tracks that intersect the Census county containing the address, for any tornado (EF0 or above) and for strong tornadoes (EF3 or above). The annual chance is a Poisson estimate from that county history: 1 − exp(−count / years). The rating in the section is FEMA’s National Risk Index tornado expected annual loss rating, which is separate from those track-based chances. The percentile bar is the tornado expected annual loss rate compared with other U.S. counties. The text also prorates historic and modeled building-loss ratios over 30 years.

About this peril

For structures, “wind peril” usually means sustained and gust wind from synoptic storms, thunderstorm downbursts, and hurricanes—not routine breezes. Engineers express design wind as a probability of exceedance (for example, roughly a 100-year return period in ASCE 7) at a standard height above ground for a given terrain exposure.

Exposure Category C is open terrain with scattered obstructions; B is urban and suburban areas; D is flat coastal and flat unobstructed plains where wind can accelerate. Taller buildings feel stronger winds than single-story homes at the same site. Hurricane wind uses the Saffir–Simpson scale and includes surge and rain; straight-line thunderstorm wind can match hurricane gusts locally without a closed cyclone circulation.

Methodology

The Wind section shows a 3-second gust at 25 feet above ground for Exposure Category C, based on the ASCE 7-22 basic wind speed from the ASCE 7 Hazard Tool (100-year mean recurrence interval, Section 26.5.2) scaled with the Exposure C K_z coefficient in Section 26.10. The cited box adds a Beaufort force and description below hurricane strength, or a plain-language Saffir–Simpson damage description at 74 mph and above (no category label). Those comparisons use conventional wind definitions and are not a formal conversion of the ASCE gust. This is not a forecast or a historic wind report.

About this peril

An earthquake releases stored stress along a fault. The magnitude describes the energy released at the source; the shaking you feel and the damage at a property depend on distance to the fault, depth, local geology, and how the building is constructed. The same magnitude event can be barely felt in one city and destructive in another.

Modified Mercalli Intensity (MMI) describes effects at a place—how people and structures respond—not the magnitude at the epicenter. At intensity VI, heavy furniture moves and plaster cracks; at VIII, ordinary frame houses can have partial collapse; at X and above, most masonry structures fail. Peak ground acceleration and spectral acceleration summarize the motion used in engineering maps; site conditions (soft soil vs rock) amplify or dampen that motion.

Aftershocks follow large mainshocks and can damage already-weakened buildings. Liquefaction, landslides, and surface fault rupture add damage beyond shaking alone in susceptible areas. Retrofit measures—anchoring cripple walls, bolting sill plates, bracing chimneys—reduce loss at intensities where the structure would otherwise fail.

Methodology

Earthquake county frequency is the FEMA National Risk Index annualized frequency for the county, cited in the same sentence as the frequency text. The Earthquake card and section order use the USGS severity-weighted 30-year shaking chance, not the NRI rating.

Chance of damaging shaking comes from the USGS National Seismic Hazard Model hazard curves at the address using the dynamic hazard service at the Vs30 from the USGS mosaic (reference values for site class labels: E 150, DE 185, D 260, CD 365, C 530, BC 760, B 1080, and A 1500 m/s). An exact midpoint keeps the softer class label shown in citations. The mosaic is the USGS global Vs30 grid (topographic slope with regional insets; https://www.usgs.gov/programs/earthquake-hazards/science/vs30-models-and-data). If that value is missing, Vs30 for hazard is inferred from topographic slope on USGS 3DEP elevations (Wald and Allen, 2007, https://doi.org/10.1785/0120060267). East of 104°W in the conterminous U.S. uses the stable-continent slope bins, and everywhere else in the model uses the active-tectonic bins. If the slope cannot be measured either, hazard uses Vs30 760 m/s (site class BC). The cited box shows the chance of intensity VI or greater, then the chance of at least one earthquake of each intensity from VI through X or higher. The rate for an intensity is the difference in annual exceedance rate between its lower and upper ground-motion boundaries. The Earthquake card and the section order use a severity-weighted form of those rates that is not shown on the page: each rate is multiplied by a relative damage weight (VI ×1, VII ×2, VIII ×4, IX ×8, X or higher ×16), the products are summed, and the sum is converted with a Poisson model over 30 years. Below 2% is Very Low, 2% to 10% is Low, 10% to 25% is Moderate, 25% to 60% is High, and above 60% is Very High. The words beside each intensity are potential damage on the USGS ShakeMap scale (Wald et al. 1999). Each boundary is the Worden et al. (2012) peak ground acceleration and 1.0-second spectral acceleration at the half-intensity. Those two exceedance rates are averaged. Intensity VI starts at the MMI 5.5 motions in the 2023 chance-of-damaging-shaking release, 0.08461 g and 0.06856 g.

About this page

The Forecasting page is separate from the address lookup. It shows live tropical outlooks, ensemble track probabilities, ENSO status, and a searchable map of historical hurricane tracks—not a property-specific rating.

Methodology

The Forecasting page shows live tropical and climate outlooks alongside the address lookup. The National Hurricane Center 7-day Atlantic Graphical Tropical Weather Outlook is the official short-range product. Current Atlantic tropical cyclone public advisories from NHC are listed beside that map; click an advisory for the full bulletin. Google Weather Lab’s public 1000-member WeatherNext Cyclones file is paired to official observed storms, so it omits invests and genesis. Forecasting prefers a locally run WeatherNext Cyclones Mini ensemble (1°, Direct Tracker with cyclogenesis) when that grid was uploaded or regenerated within the last 24 hours; when Mini is older, genesis and ensemble-only tracks from that run are merged onto the latest public 1000-member grid. If Mini has never been uploaded to storage, only the public 1000-member file is shown (no genesis). Weather Lab fallback uses precomputed 1000-member or 64-member WeatherNext 3 when live files are unreachable. Probability is the share of ensemble members with a track point inside 200 km of a 0.5° Atlantic cell at any lead in the run. Mini is coarser than the operational 0.25° 1000-member model and is experimental, not an official warning. Recent Weather Lab cycles are subject to Weather Lab’s terms of use. ECMWF’s AIFS ENS (50 members plus a control) is shown on the same 200 km / 0.5° grid, using that model’s tropical-cyclone trajectory files, which include storms that form during the forecast. AIFS is experimental, not an official warning; ECMWF open data is CC BY 4.0.

El Niño–Southern Oscillation status uses NOAA Climate Prediction Center’s Oceanic Niño Index and the latest ENSO Diagnostic Discussion. Historical hurricane tracks on Forecasting come from NOAA IBTrACS. Each storm is a simplified track whose stretches are colored by U.S. 1-minute sustained wind on the Saffir–Simpson scale at that time and place (Category 1 at 64 kt through Category 5 at 137 kt). All hurricanes in the archive are shown at once and can be filtered by peak category or year, or found by name. Choosing a search match hides the other tracks until Show all or a click on empty map. Search matches whose name was retired after that storm are shown in bold, using the WMO/NHC Atlantic and eastern/central Pacific retired-name lists. Clicking a track or choosing a search match shows that location’s category plus the storm’s name, dates, basin, and peak wind. When NOAA reports a U.S. billion-dollar tropical-cyclone loss for that name and year, the detail line also shows total direct damage in 2026 USD (CPI-adjusted from NOAA NCEI; 2026 Isaias uses published estimates).