Both radar surfaces caught this storm: NEXRAD logged 114 hail signatures up to 2.75", and the radar-estimated size reached 1.25" aloft. At 2.75" — baseball — this is severe, roof-replacing hail: close to every roof inside the footprint becomes a claim candidate.
A tornado was also reported to the National Weather Service during this storm — see the ground reports below.
2.75"
≈ baseball · the largest NEXRAD radar signature20,632
5
2 hail · 3 tornadoOverview's storm severity score weighs hailstone size, homes in the footprint, and ground-truth reports.
Largest hailstone — the top predictor of roof damage.
How many homes sit inside the storm's footprint.
Independent storm reports filed with the NWS.
We map this storm two ways: the NEXRAD radar signatures the storm produced overhead, and the radar-estimated size of the hail in the air. The two surfaces don’t have to match — where they diverge is where estimated size aloft ran ahead of, or behind, what the signatures caught.
NEXRAD radar signatures — the point detections the storm produced overhead. A signature is where the radar saw hail, not a confirmed stone on the ground.
Maximum hail size as estimated from radar aloft. Treat it as the storm's ceiling — the largest supportable stone — rather than a ground measurement.
This was Janesville's 5th recorded hail day, arriving 3 days after the Apr 14, 2026 storm. By severity it ranks 1st of the 8 storms we have logged here. Radar put the day's largest stone over Janesville at 2.75" — the largest NEXRAD radar signature.
The Apr 17, 2026 convective day was bigger than Janesville: the same system put hail over 1,016 other tracked cities, 178 of them in Wisconsin. Nearest: Milton (7 miles north, up to 2.75"); Beloit (11 miles south, up to 4"); Orfordville (11 miles west, up to 4").
These maps are stills from Janesville's Apr 17, 2026 storm. In the Overview app the same surfaces are live — radar updating in real time, radar-estimated hail size as it forms, and NWS spotter reports pinned where they're filed — with a radar replay you can scrub back over any past day.
These are storm reports filed with the National Weather Service and released through the NOAA Storm Prediction Center — public-domain observations from spotters, the public, and NWS surveys. We quote each one exactly as filed.
“NWS Damage Survey concludes an EF-1 tornado occurred with estimated peak winds of 100 mph. The tornado started southwest of Emerald Grove and moved northeastward... tak (MKX)”
— NOAA / SPC storm report
“Multiple reports of a tornado on the ground. (MKX)”
— NOAA / SPC storm report
“Corrects previous tornado report from 5 ENE Avalon. Snapped and uprooted trees... damage to houses... and sheet metal wrapped around trees near Emerald Grove. Time esti (MKX)”
— NOAA / SPC storm report
“Time estimated from radar. (MKX)”
— NOAA / SPC storm report
“(MKX)”
— NOAA / SPC storm report
The storm tracked north at roughly 15 mph, based on the timing of ground reports.
Hail was reported over 43 minutes, from to .
Reports came from Beloit and Avalon — beyond Janesville itself.
Two-inch-plus hail punctures shingles, breaks skylights and windows, and dents anything soft. In the core of a footprint like this, close to every roof is a candidate for an insurance claim. Speed decides who writes those jobs.
$248M
Potential roof exposure — 20,632 homes × the ~$12,000 industry-average hail roof claim. Exposure, not confirmed damage.Radar updates in real time, spotter reports appear on the map as they're filed, and the full Janesville storm history — this Apr 17, 2026 storm included — sits underneath. When you're ready, draw this storm's footprint and pull highly accurate homeowner contact information for every address inside it.
Highly accurate contact information starting at $0.23 per address — every contact included. Digital leads cost $15–$40. Start with a 7-day free trial — no credit card required. See pricing
8 recorded storm days in Janesville, WI
Jun 24, 2026
0.75"
Jun 10, 2026
0.5"
May 15, 2026
Apr 14, 2026
0.5"
Apr 2, 2026
2.25"
Apr 1, 2026
1"
Mar 10, 2026
0.5"