Alert archive / California / Severe Thunderstorm Warnings
Severe Thunderstorm Warnings in California, 2023
91 severe thunderstorm warnings in 2023. An alert counts here when it covered any part of the state, so the counties below add up to more than the state. The archive of severe thunderstorm warnings reaches back to 1986.
Severe Thunderstorm Warnings by county
Each county as a circle sized by its count in 2023. Tap one for its archive.
- Severe Thunderstorm Warnings
- 91
- Busiest month
- March29 severe thunderstorm warnings
- Busiest day
- August 21, 20239 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.
11 of 91 severe thunderstorm warnings covering California in 2023 had a qualifying storm report inside them; 42 of 169 hail, wind and damage reports fell inside a warning, on average 18 minutes after it went out.
California, 2023
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Severe thunderstorm warnings | 91 | 11 | 88% | 169 | 25% | 18 min |
Each office's whole area, 2023
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Hanford, CA: severe thunderstorm warnings | 24 | 2 | 92% | 41 | 24% | 15 min |
| NWS Las Vegas, NV: severe thunderstorm warnings | 52 | 6 | 88% | 37 | 22% | 21 min |
| NWS San Francisco Bay Area, CA: severe thunderstorm warnings | 3 | 2 | 33% | 58 | 12% | 23 min |
| NWS Sacramento, CA: severe thunderstorm warnings | 24 | 6 | 75% | 39 | 56% | 18 min |
| NWS Eureka, CA: severe thunderstorm warnings | 3 | 0 | 100% | 0 | ||
| NWS Los Angeles, CA: severe thunderstorm warnings | 1 | 0 | 100% | 5 | 0% | |
| NWS Medford, OR: severe thunderstorm warnings | 12 | 1 | 92% | 3 | 33% | 6 min |
| NWS San Diego, CA: severe thunderstorm warnings | 9 | 0 | 100% | 12 | 0% | |
| NWS Phoenix, AZ: severe thunderstorm warnings | 87 | 23 | 74% | 71 | 77% | 21 min |
| NWS Reno, NV: severe thunderstorm warnings | 18 | 1 | 94% | 8 | 13% | 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 | Counties | Lasted |
|---|---|---|---|---|
| Jan 4, 8:42 PM PST | Severe Thunderstorm Warning | MTR | Marin | 18 min |
| Jan 5, 2:00 PM PST | Severe Thunderstorm Warning | HNX | Tulare | 30 min |
| Jan 10, 3:28 AM PST | Severe Thunderstorm Warning | STO | Placer, Sacramento, Solano, Sutter, Yolo, Yuba | 47 min |
| Jan 10, 4:09 AM PST | Severe Thunderstorm Warning | STO | Amador, Calaveras, El Dorado, Nevada, Placer, Sacramento and 3 more | 36 min |
| Jan 10, 1:53 PM PST | Severe Thunderstorm Warning | HNX | Fresno, Madera | 37 min |
| Feb 24, 9:51 PM PST | Severe Thunderstorm Warning | LOX | Los Angeles, Ventura | 54 min |
| Mar 6, 3:49 PM PST | Severe Thunderstorm Warning | STO | Butte, Glenn | 41 min |
| Mar 6, 4:42 PM PST | Severe Thunderstorm Warning | STO | Butte, Glenn | 48 min |
| Mar 6, 5:21 PM PST | Severe Thunderstorm Warning | STO | Tehama | 24 min |
| Mar 6, 5:26 PM PST | Severe Thunderstorm Warning | STO | Butte, Tehama | 18 min |
| Mar 11, 12:42 PM PST | Severe Thunderstorm Warning | STO | San Joaquin, Stanislaus | 63 min |
| Mar 11, 1:32 PM PST | Severe Thunderstorm Warning | STO | Calaveras, San Joaquin, Stanislaus, Tuolumne | 10 min |
| Mar 11, 1:46 PM PST | Severe Thunderstorm Warning | STO | Calaveras, San Joaquin, Stanislaus, Tuolumne | 59 min |
| Mar 11, 3:09 PM PST | Severe Thunderstorm Warning | STO | Calaveras, Stanislaus | 51 min |
| Mar 11, 3:23 PM PST | Severe Thunderstorm Warning | STO | Calaveras, Stanislaus, Tuolumne | 67 min |
| Mar 11, 4:08 PM PST | Severe Thunderstorm Warning | HNX | Fresno | 37 min |
| Mar 12, 3:22 PM PDT | Severe Thunderstorm Warning | HNX | Fresno, Madera, Merced | 23 min |
| Mar 12, 3:44 PM PDT | Severe Thunderstorm Warning | HNX | Fresno, Madera, Merced | 31 min |
| Mar 12, 4:35 PM PDT | Severe Thunderstorm Warning | HNX | Fresno, Madera | 25 min |
| Mar 12, 4:58 PM PDT | Severe Thunderstorm Warning | HNX | Fresno, Madera | 32 min |
| Mar 12, 5:28 PM PDT | Severe Thunderstorm Warning | HNX | Fresno, Madera | 47 min |
| Mar 12, 6:56 PM PDT | Severe Thunderstorm Warning | HNX | Fresno, Kings, Tulare | 49 min |
| Mar 15, 2:54 PM PDT | Severe Thunderstorm Warning | VEF | San Bernardino | 36 min |
| Mar 15, 4:23 PM PDT | Severe Thunderstorm Warning | VEF | San Bernardino | 22 min |
| Mar 15, 4:26 PM PDT | Severe Thunderstorm Warning | PSR | Imperial | 34 min |
| Mar 15, 4:39 PM PDT | Severe Thunderstorm Warning | VEF | San Bernardino | 51 min |
| Mar 21, 10:26 AM PDT | Severe Thunderstorm Warning | SGX | San Diego | 49 min |
| Mar 21, 11:00 AM PDT | Severe Thunderstorm Warning | SGX | San Diego | 15 min |
| Mar 21, 12:43 PM PDT | Severe Thunderstorm Warning | MTR | Monterey | 62 min |
| Mar 21, 12:52 PM PDT | Severe Thunderstorm Warning | MTR | Santa Cruz | 38 min |
| Mar 23, 5:18 PM PDT | Severe Thunderstorm Warning | STO | Butte, Tehama | 42 min |
| Mar 23, 5:35 PM PDT | Severe Thunderstorm Warning | STO | Butte, Glenn | 55 min |
| Mar 29, 4:57 PM PDT | Severe Thunderstorm Warning | HNX | Merced | 33 min |
| Mar 30, 9:47 AM PDT | Severe Thunderstorm Warning | SGX | San Diego | 43 min |
| Mar 30, 10:33 AM PDT | Severe Thunderstorm Warning | SGX | San Diego | 27 min |
| May 6, 3:01 PM PDT | Severe Thunderstorm Warning | STO | Glenn | 29 min |
| May 6, 4:13 PM PDT | Severe Thunderstorm Warning | STO | Butte, Colusa, Glenn | 62 min |
| May 20, 4:21 PM PDT | Severe Thunderstorm Warning | HNX | Kern | 24 min |
| May 20, 6:05 PM PDT | Severe Thunderstorm Warning | SGX | San Bernardino | 55 min |
| May 20, 7:12 PM PDT | Severe Thunderstorm Warning | VEF | San Bernardino | 63 min |
| May 21, 7:53 PM PDT | Severe Thunderstorm Warning | HNX | Kern | 22 min |
| May 23, 5:29 PM PDT | Severe Thunderstorm Warning | STO | Shasta | 36 min |
| May 23, 5:51 PM PDT | Severe Thunderstorm Warning | STO | Shasta | 39 min |
| May 23, 6:35 PM PDT | Severe Thunderstorm Warning | STO | Shasta | 40 min |
| Jun 4, 4:35 PM PDT | Severe Thunderstorm Warning | REV | Lassen | 25 min |
| Jun 5, 5:56 PM PDT | Severe Thunderstorm Warning | HNX | Madera, Mariposa, Tuolumne | 34 min |
| Jun 10, 1:44 PM PDT | Severe Thunderstorm Warning | STO | Butte, Plumas, Sierra, Yuba | 46 min |
| Jun 10, 2:40 PM PDT | Severe Thunderstorm Warning | STO | Shasta | 35 min |
| Jun 10, 2:59 PM PDT | Severe Thunderstorm Warning | STO | Butte, Plumas, Tehama | 46 min |
| Jun 11, 6:30 PM PDT | Severe Thunderstorm Warning | STO | Plumas | 48 min |
| Jun 15, 10:19 PM PDT | Severe Thunderstorm Warning | VEF | Inyo | 41 min |
| Jun 16, 3:18 PM PDT | Severe Thunderstorm Warning | HNX | Tulare | 42 min |
| Jun 25, 3:51 PM PDT | Severe Thunderstorm Warning | MFR | Siskiyou | 24 min |
| Jun 25, 4:42 PM PDT | Severe Thunderstorm Warning | MFR | Siskiyou | 33 min |
| Jun 26, 5:41 PM PDT | Severe Thunderstorm Warning | MFR | Modoc | 34 min |
| Jun 26, 6:15 PM PDT | Severe Thunderstorm Warning | MFR | Siskiyou | 30 min |
| Jul 19, 4:40 PM PDT | Severe Thunderstorm Warning | REV | Mono | 50 min |
| Aug 2, 9:02 AM PDT | Severe Thunderstorm Warning | VEF | San Bernardino | 43 min |
| Aug 4, 6:09 PM PDT | Severe Thunderstorm Warning | MFR | Modoc | 36 min |
| Aug 13, 6:16 PM PDT | Severe Thunderstorm Warning | HNX | Kern | 29 min |
| Aug 15, 5:03 PM PDT | Severe Thunderstorm Warning | EKA | Humboldt, Trinity | 27 min |
| Aug 16, 2:02 PM PDT | Severe Thunderstorm Warning | SGX | San Diego | 28 min |
| Aug 16, 2:25 PM PDT | Severe Thunderstorm Warning | SGX | San Diego | 35 min |
| Aug 16, 4:31 PM PDT | Severe Thunderstorm Warning | SGX | Riverside, San Diego | 29 min |
| Aug 18, 2:29 PM PDT | Severe Thunderstorm Warning | VEF | San Bernardino | 46 min |
| Aug 18, 4:51 PM PDT | Severe Thunderstorm Warning | EKA | Trinity | 24 min |
| Aug 18, 4:57 PM PDT | Severe Thunderstorm Warning | STO | Tehama | 48 min |
| Aug 18, 5:08 PM PDT | Severe Thunderstorm Warning | PSR | Riverside, San Bernardino | 22 min |
| Aug 18, 5:32 PM PDT | Severe Thunderstorm Warning | PSR | Imperial | 28 min |
| Aug 19, 3:10 PM PDT | Severe Thunderstorm Warning | EKA | Humboldt, Mendocino, Trinity | 20 min |
| Aug 19, 6:17 PM PDT | Severe Thunderstorm Warning | STO | Shasta, Tehama | 20 min |
| Aug 20, 11:31 AM PDT | Severe Thunderstorm Warning | PSR | Imperial | 44 min |
| Aug 20, 1:00 PM PDT | Severe Thunderstorm Warning | PSR | Imperial, Riverside | 45 min |
| Aug 20, 1:07 PM PDT | Severe Thunderstorm Warning | SGX | Riverside, San Diego | 38 min |
| Aug 21, 12:35 PM PDT | Severe Thunderstorm Warning | HNX | Fresno, Merced | 25 min |
| Aug 21, 12:54 PM PDT | Severe Thunderstorm Warning | HNX | Fresno | 36 min |
| Aug 21, 1:28 PM PDT | Severe Thunderstorm Warning | HNX | Fresno, Merced | 32 min |
| Aug 21, 1:45 PM PDT | Severe Thunderstorm Warning | HNX | Merced | 30 min |
| Aug 21, 1:59 PM PDT | Severe Thunderstorm Warning | HNX | Fresno, Merced | 34 min |
| Aug 21, 2:53 PM PDT | Severe Thunderstorm Warning | HNX | Kern | 67 min |
| Aug 21, 2:56 PM PDT | Severe Thunderstorm Warning | HNX | Fresno | 24 min |
| Aug 21, 3:17 PM PDT | Severe Thunderstorm Warning | HNX | Kern | 28 min |
| Aug 21, 3:45 PM PDT | Severe Thunderstorm Warning | HNX | Kern | 30 min |
| Aug 31, 5:05 PM PDT | Severe Thunderstorm Warning | VEF | Inyo, San Bernardino | 55 min |
| Sep 1, 4:16 AM PDT | Severe Thunderstorm Warning | VEF | San Bernardino | 59 min |
| Sep 1, 12:23 PM PDT | Severe Thunderstorm Warning | PSR | Imperial | 52 min |
| Sep 1, 1:06 PM PDT | Severe Thunderstorm Warning | PSR | Imperial | 39 min |
| Sep 1, 1:37 PM PDT | Severe Thunderstorm Warning | VEF | San Bernardino | 38 min |
| Sep 1, 1:50 PM PDT | Severe Thunderstorm Warning | PSR | Imperial, Riverside | 55 min |
| Sep 1, 2:23 PM PDT | Severe Thunderstorm Warning | VEF | San Bernardino | 52 min |
| Sep 1, 5:11 PM PDT | Severe Thunderstorm Warning | VEF | Inyo, San Bernardino | 34 min |
By county
Every county with at least one alert. A county page lists each alert that covered it.
- Fresno County13
- San Bernardino County13
- Butte County8
- San Diego County8
- Madera County7
- Merced County7
- Imperial County7
- Stanislaus County6
- Tehama County6
- Kern County6
- Calaveras County5
- Tuolumne County5
- Glenn County5
- Shasta County5
- Riverside County5
- Tulare County3
- Yuba County3
- San Joaquin County3
- Plumas County3
- Inyo County3
- Siskiyou County3
- Trinity County3
- Placer County2
- Sacramento County2
- Modoc County2
- Humboldt County2
- Marin County1
- Solano County1
- Sutter County1
- Yolo County1
- Amador County1
- El Dorado County1
- Nevada County1
- Los Angeles County1
- Ventura County1
- Kings County1
- Monterey County1
- Santa Cruz County1
- Colusa County1
- Lassen County1
4 more counties
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordThe radar archive20222024
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.