Alert archive / California / Riverside County / Severe Thunderstorm Warnings
Severe Thunderstorm Warnings in Riverside County, California, 2021
15 severe thunderstorm warnings in 2021. An alert counts here when it covered this county. The archive of severe thunderstorm warnings reaches back to 1986.
Riverside County and its neighbors
Each county as a circle sized by its count in 2021. Tap one for its archive.
- Severe Thunderstorm Warnings
- 15
- Busiest month
- September6 severe thunderstorm warnings
- Busiest day
- September 9, 20214 severe thunderstorm warnings
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
4 of 15 severe thunderstorm warnings covering Riverside County in 2021 had a qualifying storm report inside them; 3 of 12 hail, wind and damage reports fell inside a warning, on average 9 minutes after it went out.
Riverside County, 2021
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Severe thunderstorm warnings | 15 | 4 | 73% | 12 | 25% | 9 min |
Each office's whole area, 2021
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS San Diego, CA: severe thunderstorm warnings | 15 | 4 | 73% | 19 | 32% | 17 min |
| NWS Phoenix, AZ: severe thunderstorm warnings | 128 | 54 | 58% | 151 | 83% | 21 min |
An office's figures cover every county it serves, including across state lines.
Verified by the Iowa Environmental Mesonet's Cow, which matches each storm-based warning with the local storm reports inside its polygon while it was in force, within 15 km of its edge: a tornado warning counts as verified on a tornado report, a severe thunderstorm warning on hail of 1 inch or more, a gust of 58 mph or more, or wind damage, a flash flood warning on a flash flood report. The false alarm ratio is the share of warnings with no such report; "inside a warning" is the probability of detection, the share of reports that fell inside one; lead time runs from the warning's issue to each report inside it, counting zero for a report that came first. A warning with no report is not proof nothing happened: reports come from spotters, the public and damage surveys, and are thin where few people live.
The alerts
Every alert, in the order issued. Times are local, Pacific Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Mar 23, 4:32 PM PDT | Severe Thunderstorm Warning | SGX | 40 min |
| Jun 23, 5:38 PM PDT | Severe Thunderstorm Warning | PSR | 37 min |
| Jul 25, 4:01 PM PDT | Severe Thunderstorm Warning | PSR | 29 min |
| Jul 25, 4:14 PM PDT | Severe Thunderstorm Warning | SGX | 36 min |
| Jul 30, 3:17 PM PDT | Severe Thunderstorm Warning | SGX | 58 min |
| Jul 30, 6:11 PM PDT | Severe Thunderstorm Warning | PSR | 79 min |
| Aug 10, 6:30 PM PDT | Severe Thunderstorm Warning | PSR | 45 min |
| Aug 10, 7:26 PM PDT | Severe Thunderstorm Warning | PSR | 49 min |
| Aug 10, 8:18 PM PDT | Severe Thunderstorm Warning | PSR | 57 min |
| Aug 31, 5:17 PM PDT | Severe Thunderstorm Warning | SGX | 58 min |
| Sep 9, 1:29 PM PDT | Severe Thunderstorm Warning | PSR | 46 min |
| Sep 9, 2:00 PM PDT | Severe Thunderstorm Warning | PSR | 45 min |
| Sep 9, 3:10 PM PDT | Severe Thunderstorm Warning | SGX | 50 min |
| Sep 9, 4:35 PM PDT | Severe Thunderstorm Warning | SGX | 55 min |
| Sep 17, 3:08 PM PDT | Severe Thunderstorm Warning | PSR | 52 min |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20202022
Sources
National Weather Service watches, warnings, advisories and statements from the Iowa Environmental Mesonet's VTEC archive, which reconstructs tornado, severe thunderstorm, flash flood and marine warnings back to 1986 from the NWS text archive. Storm Prediction Center watches and mesoscale discussions from SPC's archive through the Mesonet. County centers from the US Census Bureau. Warning verification from the Mesonet's Cow. Rebuilt daily.