The best free hail maps for roofers come straight from the federal government: the Storm Prediction Center's daily storm reports, your local National Weather Service office's storm reports, NOAA's radar-estimated hail tracks and NOAA's storm archives. Together they show where hail fell and roughly how big it was, often within hours, but none of them shows which roofs were damaged. This post compares the free sources side by side, explains what each one misses, and walks through turning a hail swath into a mailing or canvassing area.
The free government sources at a glance
All five sources below are free. They differ mainly in two ways: whether they show points (a report from one spot) or a swath (an estimate over an area), and how soon after a storm they appear.
| Source | What it shows | When it appears | Main limit |
|---|---|---|---|
| SPC storm reports | Hail reports as points with size, place and time; CSV and Google Earth (KML) files | Same day; each daily page runs from 7 a.m. to 7 a.m. Central (6 a.m. in winter) | Marked preliminary; points only |
| NWS Local Storm Reports | Reports from spotters, local officials, media and the public, issued by your local office | As your local office issues them | Preliminary until certified |
| Radar hail tracks (MESH) | Estimated largest hail size as a swath, over windows from 30 minutes to 24 hours | Updated every 2 minutes | An estimate, not measured hail |
| NCEI Severe Weather Data Inventory | Radar hail signatures and preliminary storm reports since 1995; Shapefile, KMZ and CSV | Archive, updated as needed | Radar data shows "probable conditions" |
| NCEI Storm Events Database | The official record of hail and other events, decades back | 75 to 90 days after the month ends | Hail usually a single point; accuracy not guaranteed |
A quick note on the radar product. MESH stands for Maximum Estimated Size of Hail. It comes from NOAA's Multi-Radar Multi-Sensor system, and NOAA says it is available in its MRMS Operational Product Viewer, which keeps a rolling archive back to October 2020. The track versions keep the largest estimate at each spot over a time window of up to 24 hours, which draws the hail swath. That is the closest free thing to the swath maps paid services sell.
What storm reports can and can't tell you
Storm reports come from people. The Weather Service collects them from spotters, local officials, media and the public, so they cluster where people live and drive. A 2020 study of national storm reports in the journal Weather and Forecasting notes that reports also thin out at night, when most people are asleep. The Cheyenne Weather Service office says sparse population and road networks can lead to under-reporting of severe hail in rural counties.
In practice, a gap in the reports doesn't mean no hail fell. NOAA says the same about its radar archive: missing data should not be read as a sign that no severe weather occurred there.
Reported sizes are rough too. Spotters compare hail to familiar objects, and in Cheyenne's records quarter size is the most common report, golf ball second, with the office openly asking whether golf ball hail is over-reported. Treat a reported size as a band, not a measurement.
Why 1 inch matters, and why smaller hail still counts
The Weather Service calls hail 1 inch across (about a quarter) or larger severe. It raised the threshold from 3/4 inch in January 2010, saying research showed significant damage doesn't occur from hail smaller than an inch.
Newer lab work complicates that for older roofs. In a 2025 study, researchers at the Insurance Institute for Business and Home Safety (IBHS) hit asphalt shingles with hundreds of small ice balls up to 1 inch across. Shingles that had also weathered outdoors for two years then took about ten times as much damage from large hail as new shingles; small hail without the weathering about tripled it. It was a small lab test (six products, one sample each), so read it as a direction, not a rule: an aging roof in an area that sees a lot of small hail may be in worse shape than the severe reports suggest.
Radar estimates are estimates
MESH fills the gaps between reports, but NOAA's own training page says it tends to underestimate hail size in some storm types, and that it inherits errors from the weather model behind it. When several storms pass over the same area one after another, their tracks can hide each other, and NOAA suggests shorter time windows for those cases. Use the radar swath for shape and use ground reports to check the size.
Which source to use, and when
Timing decides most of this. In the first days after a storm, SPC reports, your local storm reports and the radar tracks are what you have. The Storm Events Database, the official record, only fills in 75 to 90 days after the end of the month, so it's for history, not for this week's storm.
History is still useful. Downloading a few years of reports or radar hail signatures for your area shows which neighborhoods get hit again and again, and those are good places to look for worn roofs between storms. Our post on choosing which homes to mail covers how storm history fits with other filters such as home age.
Speed matters for mail as well. If you plan a mailing after a storm, add printing and delivery time to the data lag; our guide to how long bulk mail takes to arrive breaks that down.
How to turn a hail swath into a mailing or canvassing area
- Pull up the radar hail track for the storm day using the 24-hour window, to see the shape and direction of the swath.
- Check it against that day's SPC hail reports (the KML file opens in Google Earth). Where the radar swath shows 1 inch or more and ground reports agree, you have your core area.
- Look at the edges. Where reports are thin because few people live there, lean on the radar estimate. Where the radar shows small hail and nobody reported anything, treat it as a lower priority, not a zero.
- Turn the shape into streets or ZIP codes, then narrow it with home age and other filters so you aren't paying to reach new roofs.
- Check roofs before you spend. No hail map shows which roofs were damaged. A walk-through or an inspection does. Aerial images help narrow the list, but check the capture date: an image taken before the storm can't show its damage, though it still shows which roofs were already worn.
Right after a storm, knocking in the core area is often faster than mail; our comparison of door knocking and direct mail covers when each one wins.
When a paid hail map is worth it
Paid services package the same kind of NOAA data with alerts, swath maps and lookups by address. As of October 2026, one shingle maker's subscription tool, for example, lists hail and wind swaths, address-level reports and three years of storm history. That convenience pays off if you chase storms across many markets or need alerts the moment hail falls. If you work one metro area and can spend an hour after each storm, the free sources above cover most of what you need.
Where Scoutbound fits
A hail map tells you where hail fell, not which roofs are worn. Scoutbound looks at the roofs: in ZIP codes chosen with you, it analyzes aerial images, selects homes whose roofs show visible wear, most worn first, and mails each homeowner a personalized letter with an aerial image of their own roof, under your brand. The letter describes what the image shows in plain words and never invents damage. Postage and printing are included, and calls, texts and QR scans show up in your online portal.