Hail is the country's most expensive routine storm damage, and most of it lands on roofs. Every day since October 2020, NOAA's radar network has mapped the largest hail it estimates fell everywhere in the Lower 48. Here those swaths are laid over 85,000 census tracts to count the homes underneath: golf-ball hail (1.75 inches) and up is roof-replacement territory.
Each bar is one convective day (7 a.m. to 7 a.m. Central). The Lower-48 total always shows; pick a state above for its own days in the list below.
The hail. NOAA's Multi-Radar/Multi-Sensor system estimates the largest hail aloft at every 0.01° grid point (about 1 km) from the combined radar network (MESH, the maximum estimated size of hail). Its 24-hour maximum, 12 UTC to 12 UTC, is read for every day since October 15, 2020. MESH is a radar estimate: it tends to run larger than the stones people measure on the ground, and it can't tell a hailstorm over a field from one over a subdivision. The homes data does that part.
The homes. Census tract boundaries are drawn onto the same grid, and each tract's housing units and owner-occupied home value (ACS 2020–2024) are spread evenly across its grid cells. A swath that covers a third of a tract hits a third of its homes. "Home-hits" adds up every day, so a home hit three times counts three times. "Hit at least once" counts it once.
Why 1.75 inches. Golf-ball hail is the Weather Service's threshold for "significant" hail and roughly where asphalt shingles start needing replacement rather than repair. One-inch (quarter-size) hail, the severe-thunderstorm warning criterion, can still damage older roofs, siding and cars.