The most recent reported hail day was 2025-08-10, 355 days ago. Boulder County is hit in most years, often more than once. The largest stone on record here is 3 inches, a teacup and 3 times the National Weather Service's 1 inch severe criterion, reported on 2018-06-18 near Superior.
Colored swath = NOAA MRMS radar-estimated hail size; dots = NOAA SPC reports in Colorado. Radar-indicated, not a guarantee of damage.
The last hail here fell on 2025-08-10, around Niwot. A free SwathIQ account -- hand-reviewed, invite within 24-48h -- pulls Boulder 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 35 separate hail days here since 2010 -- 2.1 a year over 17 years of record. Those days carry 129 separate reports between them, better than three on a typical one. 3 of those 17 years produced none at all. One year dominates the record: 2018 alone produced 7 of the 35 days. The last five years track the long-run rate, with 12 days since 2022.
4 of the 35 days reached 2 inches or more -- 11%, or about one hail day in 9, the last on 2023-05-09. They land in the same month as everything else, June. Golf-ball size is rarer still: 1.75 inches or more on 6 of the 35 days.
Across the whole of Colorado, see the Colorado hail map and history.
Reports cluster nearest Longmont -- 10 of the county's 35 hail days -- then Boulder (9), Louisville (8), Niwot (6) and Erie (6). Beyond those, NOAA names Lafayette, Hygiene, Lyons, Superior, Nne Lyons, Wsw Lafayette and Marshall on more than one hail day apiece.
| Place | Hail days since 2010 | Largest stone |
|---|---|---|
| 2 N Longmont | 5 | 2.00″ |
| Louisville | 5 | 1.25″ |
| 1 N Lafayette | 3 | 2.50″ |
| Longmont | 3 | 1.75″ |
| 2 Nw Lafayette | 2 | 2.50″ |
The season runs May through July: 31 of the 35 hail days on record fall in those 3 months (89%). June is the single busiest month, with 14 of them (40%). That peak sits inside the window rather than at either end. Hail has also been reported in August and September, outside that window. Reports span 5 of the 12 calendar months; the other 7 have never produced one.
| Month | Hail days |
|---|---|
| May | 10 |
| June | 14 |
| July | 7 |
| August | 3 |
| September | 1 |
That day put 1 report on the map, the biggest 1 inch near Niwot. No hail day has been reported here yet this year.
| Date | Max hail | Reports |
|---|---|---|
| 2025-08-10 | 1.00″ | 1 |
| 2025-07-11 | 1.00″ | 1 |
| 2025-06-17 | 1.00″ | 2 |
| 2025-05-18 | 1.00″ | 1 |
| 2024-05-30 | 1.00″ | 3 |
| 2023-06-21 | 1.00″ | 1 |
| 2023-06-12 | 1.00″ | 2 |
| 2023-05-28 | 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 3 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: Jefferson County (51 hail days), Denver County (36) and Adams County (62). Every one of them takes more hail than Boulder County.
Jefferson County · Denver County · Adams County
Back to the Colorado hail map or the U.S. hail map.
Data & method: NOAA/NWS Storm Prediction Center reports + NOAA MRMS MESH radar, Boulder County, Colorado only. Radar-indicated and observation-based -- informational only, not a guarantee of damage or a valid claim.