The most recent reported hail day was 2026-04-17, 105 days ago. Jefferson County is hit in most years. The largest stone on record here is 4.25 inches and 4.2 times the National Weather Service's 1 inch severe criterion, reported on 2011-05-11 near Jefferson.
Colored swath = NOAA MRMS radar-estimated hail size; dots = NOAA SPC reports in Wisconsin. Radar-indicated, not a guarantee of damage.
The last hail here fell on 2026-04-17, around Watertown. A free SwathIQ account -- hand-reviewed, invite within 24-48h -- pulls Jefferson County addresses inside a hail swath above your size threshold into a door-knock list you can export, scoped to your approved markets.
Get free access Check an addressOur US-based call center calls the homeowners in this storm and books roof inspections straight onto your calendar. You work the storm; we fill the schedule. We dial -- you do not have to knock a single door.
See call-center options ->NOAA's Storm Prediction Center has logged 24 separate hail days here since 2010 -- 1.4 a year over 17 years of record. Those days carry 72 separate reports between them, better than three on a typical one. 4 of those 17 years produced none at all. The busiest single year was 2023, with 4 hail days. The last five years have run hotter than the long-run rate: 11 days since 2022, against 1.1 a year before that.
Roof-killing hail is routine here: 6 of the 24 days reached 2 inches or more, 25% of them, the last on 2026-04-14. They land in the same month as everything else, April. 10 of the 24 days reached golf-ball size, 1.75 inches or bigger.
Across the whole of Wisconsin, see the Wisconsin hail map and history.
Reports cluster nearest Lake Mills -- 9 of the county's 24 hail days -- then Watertown (8), Fort Atkinson (7), Johnson Creek (5) and Palmyra (5). Beyond those, NOAA names Ixonia, Jefferson, Sullivan, Lake Ripley and Waterloo on more than one hail day apiece.
| Place | Hail days since 2010 | Largest stone |
|---|---|---|
| Watertown | 4 | 1.75″ |
| Lake Mills | 4 | 1.50″ |
| Johnson Creek | 3 | 2.75″ |
| Palmyra | 3 | 1.75″ |
| 3 S Fort Atkinson | 2 | 1.75″ |
The season runs April through August: 20 of the 24 hail days on record fall in those 5 months (83%). April is the single busiest month, with 6 of them (25%). That peak opens the window: the season starts at its worst and eases off from there. Hail has also been reported in February, March, September and October, outside that window. January, November and December are the only months that have never produced a reported hail day.
| Month | Hail days |
|---|---|
| February | 1 |
| March | 1 |
| April | 6 |
| May | 6 |
| June | 4 |
| July | 2 |
| August | 2 |
| September | 1 |
| October | 1 |
That day put 1 report on the map, the biggest 1 inch near Watertown. 2 hail days have already been reported this year.
| Date | Max hail | Reports |
|---|---|---|
| 2026-04-17 | 1.00″ | 1 |
| 2026-04-14 | 2.75″ | 9 |
| 2025-05-15 | 2.50″ | 2 |
| 2025-04-18 | 2.00″ | 10 |
| 2025-04-17 | 1.00″ | 1 |
| 2024-02-08 | 1.00″ | 1 |
| 2023-10-23 | 1.00″ | 1 |
| 2023-08-24 | 1.00″ | 2 |
The colored swath is NOAA's MRMS radar estimate of the largest hail per ~1 km cell; the dots are SPC ground reports. Yellow is about an inch, red 1.5 to 2″, purple 2″ and up (hail size vs roof damage). On this county's worst day the reports reached 4.25 inches, which is the purple band. Look up a street address with the hail history by address tool.
The nearest counties with a page of their own: Waukesha County (33 hail days), Dodge County (30) and Rock County (32). Every one of them takes more hail than Jefferson County.
Waukesha County · Dodge County · Rock County
Back to the Wisconsin hail map or the U.S. hail map.
Data & method: NOAA/NWS Storm Prediction Center reports + NOAA MRMS MESH radar, Jefferson County, Wisconsin only. Radar-indicated and observation-based -- informational only, not a guarantee of damage or a valid claim.