This alert expired on 10 August 2026 at 04:34 UTC. It is kept here as a record.
It is the 2nd strongest of the 19 detections recorded within 20 km of this point since 18 April 2026. The last comparable one was on 9 August 2026. 9 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Severe Thunderstorm Warning issued August 9 at 11:25PM CDT until August 9 at 11:30PM CDT by NWS Milwaukee/Sullivan WI
An estimated 1,860,319 people live within 50 km of this point.
Nearby, since 18 April 2026
- July 27, 2026 · score 52 · 9.0 km
- July 27, 2026 · score 52 · 12.5 km
- August 11, 2026 · score 52 · 14.7 km
How we know
Confirmed by 6 independent sources, including NOAA.
Our own score for this event is 52 out of 100, at 91 % confidence.
The score is ours, computed from intensity, exposed population and local history — not the source’s.
Event Data
| Type | Severe weather |
| Severity | medium |
| Calamity Score (ours) | 52 / 100 |
| Our confidence | 91% |
| Coordinates | 42.3500, -88.2260 |
| Nearest City | McHenry (4 km) |
| Population Exposed | 1.9M within 50 km |
| Impact Tier | significant |
| Timestamp | 2026-08-10T04:25:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Severe Thunderstorm Warning_noaa_urn:oid:2.49.0.1.840.0.2857873d25ef117fc7d8f9f23f5ff89c |
Score Breakdown
Technical Details
| Event | Severe Thunderstorm Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Kenosha, WI; Racine, WI; Walworth, WI; Cook, IL; Lake, IL |
| Headline | Severe Thunderstorm Warning issued August 9 at 11:25PM CDT until August 9 at 11:30PM CDT by NWS Milwaukee/Sullivan WI |
| Expires | 2026-08-09T23:34:00-05:00 |
| SenderName | NWS Milwaukee/Sullivan WI |
| HasExactCoords | true |
| MergedCount | 2 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.2857873d25ef117fc7d8f9f23f5ff89c9280d603.001.1","noaa_urn:oid:2.49.0.1.840.0.24c32a9bf9ec81250d2ede64381dba1612f6d970.001.1"] |
| Iem TypeSummary | H |
| Iem Magnitude | 1 |
| Iem Unit | Inch |
| Iem City | 1 SSW Lake Geneva |
| Iem County | Walworth |
| Iem State | WI |
| Iem Wfo | MKX |
| MergedSources | [{"id":"iem_H_42.550_-88.400_1786335060000","source":"iem","severity":"low","severityValue":25,"timestamp":1786335060000,"latitude":42.55,"longitude":-88.4},{"id":"iem_H_42.500_-88.550_1786333800000","source":"iem","severity":"low","severityValue":25,"timestamp":1786333800000,"latitude":42.5,"longitude":-88.55},{"id":"iem_H_42.550_-88.460_1786334400000","source":"iem","severity":"low","severityValue":25,"timestamp":1786334400000,"latitude":42.55,"longitude":-88.46},{"id":"iem_H_42.240_-87.970_1786334580000","source":"iem","severity":"low","severityValue":25,"timestamp":1786334580000,"latitude":42.24,"longitude":-87.97},{"id":"iem_H_42.570_-88.440_1786334580000","source":"iem","severity":"low","severityValue":25,"timestamp":1786334580000,"latitude":42.57,"longitude":-88.44}] |
Safety Information
Always follow official guidance from your local emergency management agency. This platform provides scientific monitoring data and is not a substitute for official warnings. If you are in immediate danger, contact your local emergency number.
Series begins 10 February 2026. Comparisons refer to that period only. Collection gap: 14-26 August 2026.
This data is aggregated algorithmically from scientific sources. Not a replacement for official emergency warnings.
Want to know when something happens near McHenry?
Calamity.live data shows a weather event with CalamityScore 52/100, near McHenry (United States), based on data from noaa. Source: Calamity.live, a platform aggregating real-time data from 187 scientific monitoring sources.