The most recent reported hail day was 2025-07-17, 379 days ago. Petroleum County is hit in most years. The largest stone on record here is 3.5 inches and 3.5 times the National Weather Service's 1 inch severe criterion, reported on 2025-06-15 near Petrolia Lake.
Colored swath = NOAA MRMS radar-estimated hail size; dots = NOAA SPC reports in Montana. Radar-indicated, not a guarantee of damage.
The last hail here fell on 2025-07-17, around Petrolia Lake. A free SwathIQ account -- hand-reviewed, invite within 24-48h -- pulls Petroleum 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 30 separate hail days here since 2010 -- 1.8 a year over 17 years of record. They carry 48 reports in total: most hail days here are logged from a single spot. 5 of those 17 years produced none at all. The busiest single year was 2011, with 5 hail days. The last five years have been quieter than the long run: 6 days since 2022, against 2.0 a year before that.
5 of the 30 days reached 2 inches or more -- 17%, or about one hail day in 6, the last on 2025-07-17. They land in the same month as everything else, June. 9 of the 30 days reached golf-ball size, 1.75 inches or bigger.
Across the whole of Montana, see the Montana hail map and history.
Reports cluster nearest Winnett -- 21 of the county's 30 hail days -- then Flatwillow (8), Petrolia Lake (5) and Tiegen (2). That one town is named on 70% of them.
| Place | Hail days since 2010 | Largest stone |
|---|---|---|
| Winnett | 5 | 1.75″ |
| 3 E Petrolia Lake | 2 | 3.00″ |
| 5 Nne Winnett | 2 | 2.50″ |
| 6 S Winnett | 2 | 1.75″ |
| 4 Ene Flatwillow | 2 | 1.25″ |
The season runs June through July: 24 of the 30 hail days on record fall in those 2 months (80%). June is the single busiest month, with 13 of them (43%). Hail has also been reported in April, May and August, outside that window. Reports span 5 of the 12 calendar months; the other 7 have never produced one.
| Month | Hail days |
|---|---|
| April | 1 |
| May | 1 |
| June | 13 |
| July | 11 |
| August | 4 |
That day put 2 reports on the map, the biggest 2 inches near Petrolia Lake. No hail day has been reported here yet this year.
| Date | Max hail | Reports |
|---|---|---|
| 2025-07-17 | 2.00″ | 2 |
| 2025-06-15 | 3.50″ | 5 |
| 2025-06-13 | 1.00″ | 1 |
| 2023-07-29 | 1.00″ | 1 |
| 2022-07-14 | 1.00″ | 1 |
| 2022-07-04 | 1.00″ | 1 |
| 2021-08-26 | 1.25″ | 3 |
| 2021-06-10 | 1.00″ | 1 |
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 3.5 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: Musselshell County (30 hail days), Fergus County (48) and Golden Valley County (21). Petroleum County sits in between.
Musselshell County · Fergus County · Golden Valley County
Back to the Montana hail map or the U.S. hail map.
Data & method: NOAA/NWS Storm Prediction Center reports + NOAA MRMS MESH radar, Petroleum County, Montana only. Radar-indicated and observation-based -- informational only, not a guarantee of damage or a valid claim.