O'Brien County was hit as recently as 2026-06-27, 34 days ago. O'Brien County is hit in most years, often more than once. The largest stone on record here is 2.5 inches, a tennis ball and 2.5 times the National Weather Service's 1 inch severe criterion, reported on 2010-06-01 near Hartley.
Colored swath = NOAA MRMS radar-estimated hail size; dots = NOAA SPC reports in Iowa. Radar-indicated, not a guarantee of damage.
The last hail here fell on 2026-06-27, around Sanborn. A free SwathIQ account -- hand-reviewed, invite within 24-48h -- pulls O'Brien County addresses inside a hail swath above your size threshold into a door-knock list you can export, scoped to your approved markets.
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See call-center options ->NOAA's Storm Prediction Center has logged 34 separate hail days here since 2010 -- 2.0 a year over 17 years of record. Those days carry 63 separate reports between them, two or three on a typical one. 4 of those 17 years produced none at all. The busiest single year was 2026, with 5 hail days. The last five years have run hotter than the long-run rate: 17 days since 2022, against 1.4 a year before that.
4 of the 34 days reached 2 inches or more -- 12%, or about one hail day in 8, the last on 2025-09-22. Those big days do not follow the county's usual calendar: most of them fall in July, not May. 14 of the 34 days reached golf-ball size, 1.75 inches or bigger.
Across the whole of Iowa, see the Iowa hail map and history.
Reports cluster nearest Hartley -- 10 of the county's 34 hail days -- then Sanborn (10), Sheldon (6), Sutherland (5) and Granville (4). Beyond those, NOAA names Archer, Paullina and Primghar on more than one hail day apiece.
| Place | Hail days since 2010 | Largest stone |
|---|---|---|
| Sanborn | 8 | 1.75″ |
| Sheldon | 3 | 1.75″ |
| 4 N Sutherland | 2 | 2.00″ |
| 3 S Sanborn | 2 | 1.75″ |
| 4 SE Granville | 2 | 1.75″ |
The season runs May through September: 29 of the 34 hail days on record fall in those 5 months (85%). May is the single busiest month, with 7 of them (21%). That peak opens the window: the season starts at its worst and eases off from there. Hail has also been reported in March and April, outside that window. Reports span 7 of the 12 calendar months; the other 5 have never produced one.
| Month | Hail days |
|---|---|
| March | 1 |
| April | 4 |
| May | 7 |
| June | 7 |
| July | 5 |
| August | 5 |
| September | 5 |
That day put 1 report on the map, the biggest 1 inch near Sanborn. 5 hail days have already been reported this year.
| Date | Max hail | Reports |
|---|---|---|
| 2026-06-27 | 1.00″ | 1 |
| 2026-05-24 | 1.25″ | 1 |
| 2026-05-18 | 1.00″ | 1 |
| 2026-05-17 | 1.75″ | 1 |
| 2026-04-13 | 1.75″ | 7 |
| 2025-09-22 | 2.00″ | 4 |
| 2025-09-16 | 1.75″ | 2 |
| 2025-04-17 | 1.50″ | 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 2.5 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: Osceola County (19 hail days), Clay County (30) and Cherokee County (29). O'Brien County takes more hail than any of them.
Osceola County · Clay County · Cherokee County
Back to the Iowa hail map or the U.S. hail map.
Data & method: NOAA/NWS Storm Prediction Center reports + NOAA MRMS MESH radar, O'Brien County, Iowa only. Radar-indicated and observation-based -- informational only, not a guarantee of damage or a valid claim.