Alert archive / California / Severe Thunderstorm Warnings

Severe Thunderstorm Warnings in California, 2009

148 severe thunderstorm warnings in 2009. 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 2009. Tap one for its archive.

Severe Thunderstorm Warnings: 148
Busiest month: May40 severe thunderstorm warnings
Busiest day: June 3, 200911 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.

16 of 149 severe thunderstorm warnings covering California in 2009 had a qualifying storm report inside them; 22 of 42 hail, wind and damage reports fell inside a warning, on average 21 minutes after it went out.

California, 2009

	Warnings	With a report	False alarm ratio	Reports	Inside a warning	Mean lead time
Severe thunderstorm warnings	149	16	89%	42	52%	21 min

Each office's whole area, 2009

	Warnings	With a report	False alarm ratio	Reports	Inside a warning	Mean lead time
NWS Sacramento, CA: severe thunderstorm warnings	31	0	100%	3	0%
NWS San Diego, CA: severe thunderstorm warnings	9	1	89%	2	50%	46 min
NWS San Francisco Bay Area, CA: severe thunderstorm warnings	2	0	100%	1	0%
NWS Hanford, CA: severe thunderstorm warnings	23	11	52%	29	66%	20 min
NWS Los Angeles, CA: severe thunderstorm warnings	5	0	100%	1	0%
NWS Medford, OR: severe thunderstorm warnings	21	10	52%	30	43%	11 min
NWS Reno, NV: severe thunderstorm warnings	50	3	94%	17	47%	16 min
NWS Las Vegas, NV: severe thunderstorm warnings	53	7	87%	39	26%	17 min
NWS Phoenix, AZ: severe thunderstorm warnings	54	12	78%	37	57%	17 min
NWS Eureka, CA: severe thunderstorm warnings	20	1	95%	3	33%	11 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 24, 3:42 PM PST	Severe Thunderstorm Warning	STO	Butte, Glenn	33 min
Jan 24, 5:05 PM PST	Severe Thunderstorm Warning	STO	Tehama	25 min
Feb 5, 5:49 PM PST	Severe Thunderstorm Warning	SGX	San Diego	56 min
Feb 5, 6:46 PM PST	Severe Thunderstorm Warning	SGX	San Diego	59 min
Feb 17, 7:37 AM PST	Severe Thunderstorm Warning	MTR	Santa Clara, Santa Cruz	23 min
Mar 2, 3:05 PM PST	Severe Thunderstorm Warning	STO	Amador, Calaveras, El Dorado, Stanislaus, Tuolumne	55 min
Mar 2, 4:00 PM PST	Severe Thunderstorm Warning	STO	Calaveras, Stanislaus, Tuolumne	30 min
Mar 3, 5:34 PM PST	Severe Thunderstorm Warning	STO	Butte, Glenn, Tehama	26 min
Mar 4, 2:37 PM PST	Severe Thunderstorm Warning	STO	Shasta, Tehama	23 min
Mar 4, 2:44 PM PST	Severe Thunderstorm Warning	STO	Glenn	31 min
Mar 4, 2:59 PM PST	Severe Thunderstorm Warning	STO	Shasta, Tehama	31 min
Mar 4, 3:13 PM PST	Severe Thunderstorm Warning	STO	Glenn	47 min
Mar 4, 3:23 PM PST	Severe Thunderstorm Warning	STO	Shasta, Tehama	37 min
Mar 4, 3:59 PM PST	Severe Thunderstorm Warning	STO	Glenn	46 min
Mar 4, 4:43 PM PST	Severe Thunderstorm Warning	STO	Glenn	62 min
Mar 4, 5:27 PM PST	Severe Thunderstorm Warning	STO	Shasta, Tehama	63 min
Mar 4, 6:16 PM PST	Severe Thunderstorm Warning	HNX	Kings	29 min
Mar 4, 6:38 PM PST	Severe Thunderstorm Warning	HNX	Kings	22 min
Mar 22, 3:28 AM PDT	Severe Thunderstorm Warning	HNX	Mariposa, Merced	32 min
Apr 24, 6:10 PM PDT	Severe Thunderstorm Warning	STO	Solano	50 min
May 3, 5:28 PM PDT	Severe Thunderstorm Warning	STO	Tehama	62 min
May 18, 2:30 PM PDT	Severe Thunderstorm Warning	HNX	Kern	60 min
May 18, 3:01 PM PDT	Severe Thunderstorm Warning	HNX	Madera, Mariposa	44 min
May 18, 3:49 PM PDT	Severe Thunderstorm Warning	HNX	Mariposa, Tuolumne	56 min
May 18, 3:59 PM PDT	Severe Thunderstorm Warning	LOX	San Luis Obispo, Santa Barbara	61 min
May 18, 5:07 PM PDT	Severe Thunderstorm Warning	HNX	Tulare	30 min
May 22, 4:13 PM PDT	Severe Thunderstorm Warning	REV	Alpine	32 min
May 22, 4:48 PM PDT	Severe Thunderstorm Warning	REV	Alpine	27 min
May 22, 5:21 PM PDT	Severe Thunderstorm Warning	REV	Alpine	24 min
May 24, 5:29 PM PDT	Severe Thunderstorm Warning	REV	Lassen, Plumas	46 min
May 25, 6:42 PM PDT	Severe Thunderstorm Warning	STO	Plumas, Sierra	45 min
May 27, 3:50 PM PDT	Severe Thunderstorm Warning	STO	Shasta	20 min
May 27, 3:56 PM PDT	Severe Thunderstorm Warning	STO	Nevada, Sierra	43 min
May 27, 4:01 PM PDT	Severe Thunderstorm Warning	LOX	Santa Barbara	59 min
May 27, 4:05 PM PDT	Severe Thunderstorm Warning	STO	Shasta	31 min
May 27, 4:12 PM PDT	Severe Thunderstorm Warning	REV	Lassen	33 min
May 27, 4:24 PM PDT	Severe Thunderstorm Warning	STO	Tuolumne	66 min
May 27, 4:33 PM PDT	Severe Thunderstorm Warning	HNX	Madera	27 min
May 27, 5:12 PM PDT	Severe Thunderstorm Warning	STO	Amador, Calaveras	63 min
May 28, 2:30 PM PDT	Severe Thunderstorm Warning	LOX	San Luis Obispo, Santa Barbara	90 min
May 28, 3:19 PM PDT	Severe Thunderstorm Warning	REV	Sierra	41 min
May 28, 3:35 PM PDT	Severe Thunderstorm Warning	REV	Plumas, Sierra	40 min
May 28, 3:38 PM PDT	Severe Thunderstorm Warning	EKA	Trinity	37 min
May 28, 3:57 PM PDT	Severe Thunderstorm Warning	REV	Lassen	48 min
May 28, 4:30 PM PDT	Severe Thunderstorm Warning	EKA	Trinity	30 min
May 28, 4:56 PM PDT	Severe Thunderstorm Warning	LOX	San Luis Obispo	64 min
May 28, 4:56 PM PDT	Severe Thunderstorm Warning	REV	Lassen, Plumas	21 min
May 28, 5:37 PM PDT	Severe Thunderstorm Warning	STO	Lassen, Plumas, Shasta	44 min
May 28, 7:59 PM PDT	Severe Thunderstorm Warning	HNX	Tulare	46 min
May 28, 8:31 PM PDT	Severe Thunderstorm Warning	HNX	Fresno, Tulare	44 min
May 28, 8:45 PM PDT	Severe Thunderstorm Warning	HNX	Fresno, Kings, Tulare	45 min
May 28, 9:13 PM PDT	Severe Thunderstorm Warning	HNX	Fresno, Tulare	47 min
May 28, 9:17 PM PDT	Severe Thunderstorm Warning	HNX	Fresno, Tulare	43 min
May 28, 9:27 PM PDT	Severe Thunderstorm Warning	HNX	Fresno, Kings, Tulare	39 min
May 29, 2:47 PM PDT	Severe Thunderstorm Warning	REV	Plumas, Sierra	28 min
May 29, 5:14 PM PDT	Severe Thunderstorm Warning	HNX	Tulare	31 min
May 30, 12:52 PM PDT	Severe Thunderstorm Warning	STO	Plumas, Shasta, Tehama	24 min
May 30, 1:34 PM PDT	Severe Thunderstorm Warning	HNX	Madera	17 min
May 30, 1:35 PM PDT	Severe Thunderstorm Warning	HNX	Madera, Mariposa	40 min
May 31, 2:51 PM PDT	Severe Thunderstorm Warning	HNX	Kern	24 min
Jun 1, 1:32 PM PDT	Severe Thunderstorm Warning	REV	Mono	43 min
Jun 2, 1:49 PM PDT	Severe Thunderstorm Warning	EKA	Humboldt	17 min
Jun 2, 2:15 PM PDT	Severe Thunderstorm Warning	EKA	Del Norte	30 min
Jun 2, 2:26 PM PDT	Severe Thunderstorm Warning	EKA	Trinity	34 min
Jun 2, 2:59 PM PDT	Severe Thunderstorm Warning	EKA	Trinity	16 min
Jun 2, 5:50 PM PDT	Severe Thunderstorm Warning	STO	Shasta	40 min
Jun 2, 6:32 PM PDT	Severe Thunderstorm Warning	EKA	Mendocino	28 min
Jun 2, 8:08 PM PDT	Severe Thunderstorm Warning	STO	Tehama	37 min
Jun 3, 2:01 PM PDT	Severe Thunderstorm Warning	MFR	Modoc, Siskiyou	29 min
Jun 3, 3:21 PM PDT	Severe Thunderstorm Warning	EKA	Humboldt, Trinity	24 min
Jun 3, 3:28 PM PDT	Severe Thunderstorm Warning	EKA	Mendocino, Trinity	32 min
Jun 3, 3:44 PM PDT	Severe Thunderstorm Warning	EKA	Humboldt, Trinity	46 min
Jun 3, 4:00 PM PDT	Severe Thunderstorm Warning	EKA	Mendocino	18 min
Jun 3, 4:05 PM PDT	Severe Thunderstorm Warning	EKA	Trinity	25 min
Jun 3, 4:20 PM PDT	Severe Thunderstorm Warning	EKA	Humboldt	25 min
Jun 3, 4:47 PM PDT	Severe Thunderstorm Warning	EKA	Humboldt, Trinity	13 min
Jun 3, 5:00 PM PDT	Severe Thunderstorm Warning	EKA	Humboldt, Trinity	15 min
Jun 3, 5:17 PM PDT	Severe Thunderstorm Warning	EKA	Humboldt	13 min
Jun 3, 5:44 PM PDT	Severe Thunderstorm Warning	MTR	Alameda	31 min
Jun 3, 9:37 PM PDT	Severe Thunderstorm Warning	STO	El Dorado, Nevada, Placer, Yuba	53 min
Jun 3, 9:41 PM PDT	Severe Thunderstorm Warning	STO	Butte, Sutter, Yuba	64 min
Jun 4, 1:12 AM PDT	Severe Thunderstorm Warning	STO	Colusa, Lake	48 min
Jun 4, 11:57 PM PDT	Severe Thunderstorm Warning	HNX	Fresno	48 min
Jun 5, 12:41 AM PDT	Severe Thunderstorm Warning	HNX	Fresno, Kings, Madera	34 min
Jun 5, 1:14 AM PDT	Severe Thunderstorm Warning	HNX	Fresno, Madera	46 min
Jun 11, 6:36 PM PDT	Severe Thunderstorm Warning	STO	Tehama	54 min
Jul 2, 1:10 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	20 min
Jul 16, 5:11 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	49 min
Jul 18, 3:40 PM PDT	Severe Thunderstorm Warning	PSR	Imperial	80 min
Jul 18, 4:44 PM PDT	Severe Thunderstorm Warning	HNX	Kern	46 min
Jul 19, 5:51 PM PDT	Severe Thunderstorm Warning	SGX	San Diego	24 min
Jul 19, 6:40 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	50 min
Jul 20, 3:11 PM PDT	Severe Thunderstorm Warning	SGX	San Diego	49 min
Jul 20, 3:55 PM PDT	Severe Thunderstorm Warning	SGX	San Diego	29 min
Jul 20, 7:23 PM PDT	Severe Thunderstorm Warning	VEF	Inyo	37 min
Jul 22, 12:57 AM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	48 min
Jul 24, 2:49 PM PDT	Severe Thunderstorm Warning	PSR	Imperial	41 min
Jul 24, 3:03 PM PDT	Severe Thunderstorm Warning	PSR	Riverside	42 min
Jul 24, 4:44 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	46 min
Jul 25, 2:44 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	46 min
Jul 28, 3:30 PM PDT	Severe Thunderstorm Warning	REV	Alpine, Mono	30 min
Jul 28, 3:32 PM PDT	Severe Thunderstorm Warning	HNX	Madera, Mariposa, Tuolumne	35 min
Jul 28, 3:50 PM PDT	Severe Thunderstorm Warning	REV	Nevada, Sierra	40 min
Jul 28, 4:22 PM PDT	Severe Thunderstorm Warning	STO	Lassen, Plumas, Shasta, Tehama	29 min
Jul 28, 7:00 PM PDT	Severe Thunderstorm Warning	REV	Alpine, El Dorado	60 min
Jul 28, 7:32 PM PDT	Severe Thunderstorm Warning	REV	Sierra	28 min
Jul 29, 1:55 PM PDT	Severe Thunderstorm Warning	STO	Plumas	35 min
Jul 29, 2:57 PM PDT	Severe Thunderstorm Warning	REV	Alpine, Mono	33 min
Jul 29, 8:27 PM PDT	Severe Thunderstorm Warning	REV	Lassen	48 min
Jul 30, 2:26 PM PDT	Severe Thunderstorm Warning	REV	Placer	49 min
Jul 30, 4:30 PM PDT	Severe Thunderstorm Warning	REV	Alpine, Mono	45 min
Jul 30, 4:42 PM PDT	Severe Thunderstorm Warning	REV	Mono	33 min
Jul 30, 4:53 PM PDT	Severe Thunderstorm Warning	REV	Lassen, Plumas	52 min
Jul 30, 5:11 PM PDT	Severe Thunderstorm Warning	REV	Lassen, Sierra	49 min
Jul 30, 6:44 PM PDT	Severe Thunderstorm Warning	REV	Lassen, Plumas	46 min
Jul 31, 2:53 PM PDT	Severe Thunderstorm Warning	REV	Alpine, Mono	37 min
Jul 31, 6:34 PM PDT	Severe Thunderstorm Warning	REV	Lassen	26 min
Aug 2, 3:26 PM PDT	Severe Thunderstorm Warning	MFR	Modoc	49 min
Aug 2, 4:15 PM PDT	Severe Thunderstorm Warning	EKA	Del Norte	30 min
Aug 2, 6:46 PM PDT	Severe Thunderstorm Warning	REV	Lassen, Sierra	32 min
Aug 2, 7:00 PM PDT	Severe Thunderstorm Warning	REV	Lassen, Plumas	30 min
Aug 5, 5:41 PM PDT	Severe Thunderstorm Warning	EKA	Trinity	34 min
Aug 5, 6:11 PM PDT	Severe Thunderstorm Warning	EKA	Humboldt, Trinity	19 min
Aug 5, 6:29 PM PDT	Severe Thunderstorm Warning	EKA	Humboldt, Trinity	16 min
Aug 22, 4:29 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	46 min
Aug 22, 5:14 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	46 min
Aug 22, 6:00 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	30 min
Aug 23, 4:13 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	47 min
Aug 23, 4:23 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	37 min
Aug 23, 4:53 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	37 min
Aug 23, 4:57 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	34 min
Aug 23, 6:11 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	30 min
Aug 23, 7:24 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	36 min
Aug 23, 7:56 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	34 min
Sep 1, 2:53 PM PDT	Severe Thunderstorm Warning	SGX	San Diego	37 min
Sep 2, 3:24 PM PDT	Severe Thunderstorm Warning	SGX	San Diego	38 min
Sep 2, 4:19 PM PDT	Severe Thunderstorm Warning	SGX	Orange, Riverside	26 min
Sep 2, 6:13 PM PDT	Severe Thunderstorm Warning	PSR	Riverside	22 min
Sep 5, 3:25 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	50 min
Sep 5, 3:36 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	54 min
Sep 5, 4:44 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	61 min
Sep 5, 4:50 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	55 min
Sep 5, 5:00 PM PDT	Severe Thunderstorm Warning	SGX	San Diego	60 min
Sep 5, 5:45 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	60 min
Sep 5, 5:49 PM PDT	Severe Thunderstorm Warning	VEF	San Bernardino	26 min
Sep 5, 6:04 PM PDT	Severe Thunderstorm Warning	PSR	Imperial	25 min
Sep 12, 4:08 PM PDT	Severe Thunderstorm Warning	REV	Lassen, Plumas	22 min
Dec 13, 12:45 AM PST	Severe Thunderstorm Warning	LOX	San Luis Obispo, Santa Barbara	60 min

The busiest days

Days with the most alerts issued, by UTC date.

Nearby

Alerts in force now Tornadoes on record The radar archive 2008 2010

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.