The morning after a hailstorm, half the roofers in town are looking at the same coloured blob on the same map. The other half are driving around looking for dented gutters.

A hail map for roofers is weather radar's estimate of how large the hail was over each patch of ground, usually checked against storm reports from people who saw it fall. It tells you which streets most likely took hail and roughly how big it was. It does not tell you which roofs are damaged. Used that way, as a list of where to look first, it is the most useful thing a storm roofer has. Used as proof of damage, it gets people in trouble.

Where does hail map data come from?

Nearly every hail map on the market is built from the same public sources, then cleaned up and drawn differently.

  • Weather radar. The National Weather Service radar network scans storms every few minutes. NOAA's Multi-Radar Multi-Sensor system blends many radars with other observations into products for hail, wind and rain. Hail size estimates come from how strongly the storm reflects the radar beam at different heights.
  • Storm reports. Spotters, emergency managers and the public report hail as it falls, and the Storm Prediction Center publishes them as daily storm reports. They are preliminary on the day and get cleaned up later into NOAA's Storm Events Database.

Radar gives you coverage everywhere. Reports give you ground truth in a few places. A good map uses both, and tells you which one a given dot came from.

How accurate are hail maps for finding damaged roofs?

Accurate enough to choose neighbourhoods, not accurate enough to promise anything about a single house. Three reasons:

  • Radar sees hail in the air, not on the shingles. Stones melt on the way down, wind pushes them sideways, and the estimate is for an area, not a rooftop.
  • Reports follow people. Storm reports cluster along highways and in towns. A rural swath with no reports can still have taken big hail.
  • Roofs differ. The same stone that bruises a twenty-year-old three-tab roof might do nothing to a new impact-rated one next door.
A thick layer of white hailstones piled on the ground after a storm
The map shows where stones like these likely fell. Only an inspection shows what they did.

None of that makes the map less useful. Hail is common enough that guessing is expensive: the Insurance Information Institute, citing NOAA's Storm Prediction Center, counts more than 5,400 hail events in 2025, with Texas well ahead of every other state. The point is to treat the map as a ranking of streets, then let an inspection decide each roof.

How should a roofer use a hail map after a storm?

Start with the map, then narrow it with things the map does not know.

  1. Pull the swath for the storm. Note the hail size bands, and where reports confirm them.
  2. Put homes on it. A swath over a field is not work. A swath over three subdivisions is. If you can, add the size of each roof too, which can now be measured without climbing, so you know which homes are the big jobs.
  3. Add roof age. Re-roof permit records tell you which homes had a new roof recently. A roof with fresh hail and no permit on file is usually the first one to call.
  4. Rank, then route. Biggest hail on the oldest roofs first, in an order a person can actually drive. We cover the routing half in how to plan a door-knocking route after a hailstorm.
  5. Inspect before you say anything about damage. The map earns you the conversation. The ladder decides the job.
Free check

Look up yesterday's storm on the Storm Prediction Center's daily report page, then check the same date in the Storm Events Database a few weeks later. Watching how the reports change between the two tells you a lot about how much to trust any single dot on a map.

What can a hail map not tell you?

Whether the roof is damaged. Whether the homeowner has already signed with someone. Whether an insurer will pay. That last one matters: a hail map is never a reason to tell a homeowner their claim will be approved or their deductible handled, and a roofer who says either is the one homeowners get warned about on the local news.

It also cannot tell you who else has been on the street. After a big storm, the first neighbourhoods on every map fill up with trucks by lunchtime. Homes a little further down the swath, with older roofs and less famous hail, are often the better day's work.

How Roof Command uses hail data

Roof Command lays weather-radar hail estimates over every home in your service area, checked against local storm reports, going back to October 2020 and updated each morning. Each home carries its hail history, roof size and re-roof permit record, and the hardest-hit homes with the oldest roofs become the Daily 50: a call list and knock route for a person on your team. It tells you where to look first, not what you will find on the roof, and we say so in writing.