Transparent Methodology
Every HailScore is built from verified NOAA radar data. Not estimates, not models. Here is exactly how we turn 4.5 million storm records into a risk score for your address.
4.5M+
Radar Records
NOAA NEXRAD hail events
10 Yrs
of Data
2015 through 2025
50
States
Nationwide coverage
$0
Your Cost
Always free for homeowners
HailScore is built on official NOAA government data, the same data used by meteorologists, insurance actuaries, and the National Weather Service.
The Next Generation Weather Radar network operates 160 high resolution Doppler radar stations across the US. These stations use dual polarization technology to detect precipitation type, intensity, and movement. When storm cells produce hail, NEXRAD measures estimated hail diameter and logs the event with precise coordinates and timestamp.
The SWDI API maintained by NCEI provides structured access to storm event records. We ingest hail event records via the SWDI API endpoint, filtering for hail events with diameter of 0.75 inches or larger within each city bounding box.
The NOAA Storm Events Database provides ground-truth verification for major hail events, including reports from storm spotters, emergency management, and law enforcement. We cross-reference NEXRAD detections with Storm Events data to validate the largest events in our database.
Five weighted factors combine to produce your 0 to 100 HailScore. Each factor reflects a distinct dimension of hail damage risk.
Weight breakdown
We count every radar-detected hail event within 15 miles of your property over the past 10 years. More events = higher base score.
Recent storms score higher than old ones. We apply an exponential time decay function. A storm from last month counts roughly 3x more than one from five years ago.
Hail size scales non-linearly. Under 0.75 inches is negligible. 1 to 1.5 inches is moderate. 1.75 to 2 inches is significant. Over 2 inches means severe structural damage likely requiring full replacement.
Repeated moderate hail compounds over time. A roof hit by 1" hail five times has accumulated more damage than one hit once by 2" hail.
A storm 0.1 miles away scores at full weight; one at 14 miles scores at roughly 10% weight. We use a distance-decay function based on storm cell size from NEXRAD data.
HailScores range from 0 to 100. Here is what each band means for your property.
0-30
Low Risk
Minimal hail history. Standard roof maintenance is sufficient.
31-60
Moderate Risk
Some hail activity. Consider an inspection after any 1"+ event.
61-80
High Risk
Regular hail exposure. Professional inspection strongly recommended.
81-100
Very High Risk
Severe, repeated hail history. Roof damage is likely. Inspect immediately.
From NOAA radar detection to your HailScore. The data pipeline explained.
NOAA radar stations scan the atmosphere every 4 to 6 minutes. When storm cells produce hail, the dual polarization radar detects the hail signature and logs estimated diameter, timestamp, and precise coordinates.
We pull hail event records from the NOAA SWDI API for all cities in our database, filtering for events 0.75 inch diameter and above. Records are loaded into a PostGIS spatial database for fast geographic queries.
Each hail event is stored as a geographic point in our database. When you look up an address, we run a spatial query to find all events within 15 miles of your coordinates. Results typically come back in under 200ms.
The five scoring factors (frequency, recency, hail size, cumulative damage, proximity) are computed from the query results and normalized to a 0 to 100 scale. Score calculation happens server side in real time.
Your full report includes the numeric score, score band, storm event timeline, interactive map, hail size distribution, and a summary of the highest impact events near your property.
Now that you know how it works, enter your address and see exactly what storms have hit near your home. Free, instant, no signup required.
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