About the Data

Where the data comes from

IDOLCheck storm activity pages are built from two official National Oceanic and Atmospheric Administration (NOAA) sources:

• SPC verified storm reports — Local Storm Reports collected by the NOAA Storm Prediction Center from trained spotters, emergency managers, and National Weather Service offices. Each report carries a hazard type (hail, wind, tornado), a measured magnitude where available (hail diameter in inches, wind gust in mph), a time, and a location.
• NWS severe weather warnings — Severe Thunderstorm and Tornado Warnings issued by National Weather Service forecast offices, including the hail size and wind speed the forecaster cited in the warning text and the polygon boundary the warning covered.

Both feeds are ingested, normalized, and geocoded by HailyDB, the storm data engine that powers IDOLCheck. IDOLCheck reads from HailyDB; it does not edit, estimate, or model storm records.

What counts as an event

A county page lists an event when an SPC report or NWS warning is attributed to that county. Wind is included at 50 mph and above (the NWS severe threshold is 58 mph; 50 mph captures the strong-gust reports spotters file below it). Any hail report with a measured size is included. Every tornado report is included. A warning that covered several counties appears on each of those county pages, because each was genuinely under the warning.

The 12 months window

Pages cover a rolling 12 months. Totals, peak magnitudes, leaderboards, and the day-by-day storm log all recalculate from the same window, refreshed from HailyDB every few hours. The national state rankings use the same rolling year of SPC reports.

Why the last 30 days show less detail

Events from the most recent 30 days are shown at county level with month-only dates: how many reports, what hazard, and the peak magnitude, but not the exact day, location, warning text, or radar snapshot. Once a storm day passes the 30-day mark its full detail unlocks on the public page. Exact recent detail, address-level checks, and warning-boundary containment are available in the IDOLCheck app with a free account. This is how we keep the public record complete while keeping the app worth signing into.

How the national rankings work

The hub ranks all 50 states two ways, both from SPC verified reports over the rolling 12 months:

• By report frequency — a plain count of wind, hail, and tornado reports. This rewards dense spotter coverage and derechos, which can generate hundreds of wind reports in a single afternoon.
• By severity-weighted index — each report is weighted by hazard: tornado ×20, hail ×4, wind ×1. This is our own weighting, disclosed wherever the index appears, and it exists so one derecho's wind reports do not outrank a tornado outbreak.

Radar imagery

Radar snapshots are NEXRAD composites rendered by the Iowa Environmental Mesonet (Iowa State University) for the time of the event shown. They are archival images of what the radar saw, not forecasts.

Tornado ratings

SPC preliminary reports rarely carry an EF rating. Final Enhanced Fujita ratings are assigned by NWS survey teams after ground surveys and published later in NOAA's Storm Events database. Our pages report tornado counts; where a rating is shown it comes from the official record.

Where AI is — and is not — involved

Every storm event, magnitude, date, and radar image is deterministic: retrieved from the official record and displayed as reported. Quoted warning text is always attributed to its source. Where the surrounding prose is not a quote, it was drafted with AI assistance from that same verified data and reviewed and approved by humans before publication. AI organizes and presents the record. It never invents storm data, and nothing on these pages is a forecast.

Limitations

• SPC reports depend on someone observing and reporting the hazard. Rural counties are under-reported relative to what actually fell.
• A report's county is the county the observer recorded. Storms cross lines; a report a mile inside a neighbor county counts there.
• Warning-cited hail and wind values are what the forecaster expected, not a ground measurement. We label them as NWS severe weather mentions to keep that distinction visible.
• These pages are informational and are not a substitute for verifying official storm records.