How the hail map works

Radar hail estimates

Hail sizes come from MESH (Maximum Estimated Size of Hail), part of NOAA's Multi-Radar Multi-Sensor (MRMS) system run by the National Severe Storms Laboratory. MESH combines data from several radars to estimate the largest hail at each point on a grid about one kilometer across. We use the 24-hour maximum product, archived by the Iowa Environmental Mesonet, and assign each storm to the local date it fell.

Ground reports

Where available, we add National Weather Service local storm reports: hail of three quarters of an inch or more, damaging wind, and tornadoes. These are observations, but most hail is never reported.

Zip codes

Zip boundaries are 2020 Census ZIP Code Tabulation Areas. Each zip shows the largest estimate anywhere inside its boundary, and the share of the zip that saw one inch or more.

Limits

MESH is an estimate. It can run larger or smaller than the hail that reached the ground, and it says nothing about the condition of a particular roof. Use this map to know when to look, then have the roof inspected.