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

WarningsWith a reportFalse alarm ratioReportsInside a warningMean lead time
Severe thunderstorm warnings1491689%4252%21 min

Each office's whole area, 2009

WarningsWith a reportFalse alarm ratioReportsInside a warningMean lead time
NWS Sacramento, CA: severe thunderstorm warnings310100%30%
NWS San Diego, CA: severe thunderstorm warnings9189%250%46 min
NWS San Francisco Bay Area, CA: severe thunderstorm warnings20100%10%
NWS Hanford, CA: severe thunderstorm warnings231152%2966%20 min
NWS Los Angeles, CA: severe thunderstorm warnings50100%10%
NWS Medford, OR: severe thunderstorm warnings211052%3043%11 min
NWS Reno, NV: severe thunderstorm warnings50394%1747%16 min
NWS Las Vegas, NV: severe thunderstorm warnings53787%3926%17 min
NWS Phoenix, AZ: severe thunderstorm warnings541278%3757%17 min
NWS Eureka, CA: severe thunderstorm warnings20195%333%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.

IssuedProductOfficeCountiesLasted
Jan 24, 3:42 PM PSTSevere Thunderstorm WarningSTOButte, Glenn33 min
Jan 24, 5:05 PM PSTSevere Thunderstorm WarningSTOTehama25 min
Feb 5, 5:49 PM PSTSevere Thunderstorm WarningSGXSan Diego56 min
Feb 5, 6:46 PM PSTSevere Thunderstorm WarningSGXSan Diego59 min
Feb 17, 7:37 AM PSTSevere Thunderstorm WarningMTRSanta Clara, Santa Cruz23 min
Mar 2, 3:05 PM PSTSevere Thunderstorm WarningSTOAmador, Calaveras, El Dorado, Stanislaus, Tuolumne55 min
Mar 2, 4:00 PM PSTSevere Thunderstorm WarningSTOCalaveras, Stanislaus, Tuolumne30 min
Mar 3, 5:34 PM PSTSevere Thunderstorm WarningSTOButte, Glenn, Tehama26 min
Mar 4, 2:37 PM PSTSevere Thunderstorm WarningSTOShasta, Tehama23 min
Mar 4, 2:44 PM PSTSevere Thunderstorm WarningSTOGlenn31 min
Mar 4, 2:59 PM PSTSevere Thunderstorm WarningSTOShasta, Tehama31 min
Mar 4, 3:13 PM PSTSevere Thunderstorm WarningSTOGlenn47 min
Mar 4, 3:23 PM PSTSevere Thunderstorm WarningSTOShasta, Tehama37 min
Mar 4, 3:59 PM PSTSevere Thunderstorm WarningSTOGlenn46 min
Mar 4, 4:43 PM PSTSevere Thunderstorm WarningSTOGlenn62 min
Mar 4, 5:27 PM PSTSevere Thunderstorm WarningSTOShasta, Tehama63 min
Mar 4, 6:16 PM PSTSevere Thunderstorm WarningHNXKings29 min
Mar 4, 6:38 PM PSTSevere Thunderstorm WarningHNXKings22 min
Mar 22, 3:28 AM PDTSevere Thunderstorm WarningHNXMariposa, Merced32 min
Apr 24, 6:10 PM PDTSevere Thunderstorm WarningSTOSolano50 min
May 3, 5:28 PM PDTSevere Thunderstorm WarningSTOTehama62 min
May 18, 2:30 PM PDTSevere Thunderstorm WarningHNXKern60 min
May 18, 3:01 PM PDTSevere Thunderstorm WarningHNXMadera, Mariposa44 min
May 18, 3:49 PM PDTSevere Thunderstorm WarningHNXMariposa, Tuolumne56 min
May 18, 3:59 PM PDTSevere Thunderstorm WarningLOXSan Luis Obispo, Santa Barbara61 min
May 18, 5:07 PM PDTSevere Thunderstorm WarningHNXTulare30 min
May 22, 4:13 PM PDTSevere Thunderstorm WarningREVAlpine32 min
May 22, 4:48 PM PDTSevere Thunderstorm WarningREVAlpine27 min
May 22, 5:21 PM PDTSevere Thunderstorm WarningREVAlpine24 min
May 24, 5:29 PM PDTSevere Thunderstorm WarningREVLassen, Plumas46 min
May 25, 6:42 PM PDTSevere Thunderstorm WarningSTOPlumas, Sierra45 min
May 27, 3:50 PM PDTSevere Thunderstorm WarningSTOShasta20 min
May 27, 3:56 PM PDTSevere Thunderstorm WarningSTONevada, Sierra43 min
May 27, 4:01 PM PDTSevere Thunderstorm WarningLOXSanta Barbara59 min
May 27, 4:05 PM PDTSevere Thunderstorm WarningSTOShasta31 min
May 27, 4:12 PM PDTSevere Thunderstorm WarningREVLassen33 min
May 27, 4:24 PM PDTSevere Thunderstorm WarningSTOTuolumne66 min
May 27, 4:33 PM PDTSevere Thunderstorm WarningHNXMadera27 min
May 27, 5:12 PM PDTSevere Thunderstorm WarningSTOAmador, Calaveras63 min
May 28, 2:30 PM PDTSevere Thunderstorm WarningLOXSan Luis Obispo, Santa Barbara90 min
May 28, 3:19 PM PDTSevere Thunderstorm WarningREVSierra41 min
May 28, 3:35 PM PDTSevere Thunderstorm WarningREVPlumas, Sierra40 min
May 28, 3:38 PM PDTSevere Thunderstorm WarningEKATrinity37 min
May 28, 3:57 PM PDTSevere Thunderstorm WarningREVLassen48 min
May 28, 4:30 PM PDTSevere Thunderstorm WarningEKATrinity30 min
May 28, 4:56 PM PDTSevere Thunderstorm WarningLOXSan Luis Obispo64 min
May 28, 4:56 PM PDTSevere Thunderstorm WarningREVLassen, Plumas21 min
May 28, 5:37 PM PDTSevere Thunderstorm WarningSTOLassen, Plumas, Shasta44 min
May 28, 7:59 PM PDTSevere Thunderstorm WarningHNXTulare46 min
May 28, 8:31 PM PDTSevere Thunderstorm WarningHNXFresno, Tulare44 min
May 28, 8:45 PM PDTSevere Thunderstorm WarningHNXFresno, Kings, Tulare45 min
May 28, 9:13 PM PDTSevere Thunderstorm WarningHNXFresno, Tulare47 min
May 28, 9:17 PM PDTSevere Thunderstorm WarningHNXFresno, Tulare43 min
May 28, 9:27 PM PDTSevere Thunderstorm WarningHNXFresno, Kings, Tulare39 min
May 29, 2:47 PM PDTSevere Thunderstorm WarningREVPlumas, Sierra28 min
May 29, 5:14 PM PDTSevere Thunderstorm WarningHNXTulare31 min
May 30, 12:52 PM PDTSevere Thunderstorm WarningSTOPlumas, Shasta, Tehama24 min
May 30, 1:34 PM PDTSevere Thunderstorm WarningHNXMadera17 min
May 30, 1:35 PM PDTSevere Thunderstorm WarningHNXMadera, Mariposa40 min
May 31, 2:51 PM PDTSevere Thunderstorm WarningHNXKern24 min
Jun 1, 1:32 PM PDTSevere Thunderstorm WarningREVMono43 min
Jun 2, 1:49 PM PDTSevere Thunderstorm WarningEKAHumboldt17 min
Jun 2, 2:15 PM PDTSevere Thunderstorm WarningEKADel Norte30 min
Jun 2, 2:26 PM PDTSevere Thunderstorm WarningEKATrinity34 min
Jun 2, 2:59 PM PDTSevere Thunderstorm WarningEKATrinity16 min
Jun 2, 5:50 PM PDTSevere Thunderstorm WarningSTOShasta40 min
Jun 2, 6:32 PM PDTSevere Thunderstorm WarningEKAMendocino28 min
Jun 2, 8:08 PM PDTSevere Thunderstorm WarningSTOTehama37 min
Jun 3, 2:01 PM PDTSevere Thunderstorm WarningMFRModoc, Siskiyou29 min
Jun 3, 3:21 PM PDTSevere Thunderstorm WarningEKAHumboldt, Trinity24 min
Jun 3, 3:28 PM PDTSevere Thunderstorm WarningEKAMendocino, Trinity32 min
Jun 3, 3:44 PM PDTSevere Thunderstorm WarningEKAHumboldt, Trinity46 min
Jun 3, 4:00 PM PDTSevere Thunderstorm WarningEKAMendocino18 min
Jun 3, 4:05 PM PDTSevere Thunderstorm WarningEKATrinity25 min
Jun 3, 4:20 PM PDTSevere Thunderstorm WarningEKAHumboldt25 min
Jun 3, 4:47 PM PDTSevere Thunderstorm WarningEKAHumboldt, Trinity13 min
Jun 3, 5:00 PM PDTSevere Thunderstorm WarningEKAHumboldt, Trinity15 min
Jun 3, 5:17 PM PDTSevere Thunderstorm WarningEKAHumboldt13 min
Jun 3, 5:44 PM PDTSevere Thunderstorm WarningMTRAlameda31 min
Jun 3, 9:37 PM PDTSevere Thunderstorm WarningSTOEl Dorado, Nevada, Placer, Yuba53 min
Jun 3, 9:41 PM PDTSevere Thunderstorm WarningSTOButte, Sutter, Yuba64 min
Jun 4, 1:12 AM PDTSevere Thunderstorm WarningSTOColusa, Lake48 min
Jun 4, 11:57 PM PDTSevere Thunderstorm WarningHNXFresno48 min
Jun 5, 12:41 AM PDTSevere Thunderstorm WarningHNXFresno, Kings, Madera34 min
Jun 5, 1:14 AM PDTSevere Thunderstorm WarningHNXFresno, Madera46 min
Jun 11, 6:36 PM PDTSevere Thunderstorm WarningSTOTehama54 min
Jul 2, 1:10 PM PDTSevere Thunderstorm WarningVEFSan Bernardino20 min
Jul 16, 5:11 PM PDTSevere Thunderstorm WarningVEFSan Bernardino49 min
Jul 18, 3:40 PM PDTSevere Thunderstorm WarningPSRImperial80 min
Jul 18, 4:44 PM PDTSevere Thunderstorm WarningHNXKern46 min
Jul 19, 5:51 PM PDTSevere Thunderstorm WarningSGXSan Diego24 min
Jul 19, 6:40 PM PDTSevere Thunderstorm WarningVEFSan Bernardino50 min
Jul 20, 3:11 PM PDTSevere Thunderstorm WarningSGXSan Diego49 min
Jul 20, 3:55 PM PDTSevere Thunderstorm WarningSGXSan Diego29 min
Jul 20, 7:23 PM PDTSevere Thunderstorm WarningVEFInyo37 min
Jul 22, 12:57 AM PDTSevere Thunderstorm WarningVEFSan Bernardino48 min
Jul 24, 2:49 PM PDTSevere Thunderstorm WarningPSRImperial41 min
Jul 24, 3:03 PM PDTSevere Thunderstorm WarningPSRRiverside42 min
Jul 24, 4:44 PM PDTSevere Thunderstorm WarningVEFSan Bernardino46 min
Jul 25, 2:44 PM PDTSevere Thunderstorm WarningVEFSan Bernardino46 min
Jul 28, 3:30 PM PDTSevere Thunderstorm WarningREVAlpine, Mono30 min
Jul 28, 3:32 PM PDTSevere Thunderstorm WarningHNXMadera, Mariposa, Tuolumne35 min
Jul 28, 3:50 PM PDTSevere Thunderstorm WarningREVNevada, Sierra40 min
Jul 28, 4:22 PM PDTSevere Thunderstorm WarningSTOLassen, Plumas, Shasta, Tehama29 min
Jul 28, 7:00 PM PDTSevere Thunderstorm WarningREVAlpine, El Dorado60 min
Jul 28, 7:32 PM PDTSevere Thunderstorm WarningREVSierra28 min
Jul 29, 1:55 PM PDTSevere Thunderstorm WarningSTOPlumas35 min
Jul 29, 2:57 PM PDTSevere Thunderstorm WarningREVAlpine, Mono33 min
Jul 29, 8:27 PM PDTSevere Thunderstorm WarningREVLassen48 min
Jul 30, 2:26 PM PDTSevere Thunderstorm WarningREVPlacer49 min
Jul 30, 4:30 PM PDTSevere Thunderstorm WarningREVAlpine, Mono45 min
Jul 30, 4:42 PM PDTSevere Thunderstorm WarningREVMono33 min
Jul 30, 4:53 PM PDTSevere Thunderstorm WarningREVLassen, Plumas52 min
Jul 30, 5:11 PM PDTSevere Thunderstorm WarningREVLassen, Sierra49 min
Jul 30, 6:44 PM PDTSevere Thunderstorm WarningREVLassen, Plumas46 min
Jul 31, 2:53 PM PDTSevere Thunderstorm WarningREVAlpine, Mono37 min
Jul 31, 6:34 PM PDTSevere Thunderstorm WarningREVLassen26 min
Aug 2, 3:26 PM PDTSevere Thunderstorm WarningMFRModoc49 min
Aug 2, 4:15 PM PDTSevere Thunderstorm WarningEKADel Norte30 min
Aug 2, 6:46 PM PDTSevere Thunderstorm WarningREVLassen, Sierra32 min
Aug 2, 7:00 PM PDTSevere Thunderstorm WarningREVLassen, Plumas30 min
Aug 5, 5:41 PM PDTSevere Thunderstorm WarningEKATrinity34 min
Aug 5, 6:11 PM PDTSevere Thunderstorm WarningEKAHumboldt, Trinity19 min
Aug 5, 6:29 PM PDTSevere Thunderstorm WarningEKAHumboldt, Trinity16 min
Aug 22, 4:29 PM PDTSevere Thunderstorm WarningVEFSan Bernardino46 min
Aug 22, 5:14 PM PDTSevere Thunderstorm WarningVEFSan Bernardino46 min
Aug 22, 6:00 PM PDTSevere Thunderstorm WarningVEFSan Bernardino30 min
Aug 23, 4:13 PM PDTSevere Thunderstorm WarningVEFSan Bernardino47 min
Aug 23, 4:23 PM PDTSevere Thunderstorm WarningVEFSan Bernardino37 min
Aug 23, 4:53 PM PDTSevere Thunderstorm WarningVEFSan Bernardino37 min
Aug 23, 4:57 PM PDTSevere Thunderstorm WarningVEFSan Bernardino34 min
Aug 23, 6:11 PM PDTSevere Thunderstorm WarningVEFSan Bernardino30 min
Aug 23, 7:24 PM PDTSevere Thunderstorm WarningVEFSan Bernardino36 min
Aug 23, 7:56 PM PDTSevere Thunderstorm WarningVEFSan Bernardino34 min
Sep 1, 2:53 PM PDTSevere Thunderstorm WarningSGXSan Diego37 min
Sep 2, 3:24 PM PDTSevere Thunderstorm WarningSGXSan Diego38 min
Sep 2, 4:19 PM PDTSevere Thunderstorm WarningSGXOrange, Riverside26 min
Sep 2, 6:13 PM PDTSevere Thunderstorm WarningPSRRiverside22 min
Sep 5, 3:25 PM PDTSevere Thunderstorm WarningVEFSan Bernardino50 min
Sep 5, 3:36 PM PDTSevere Thunderstorm WarningVEFSan Bernardino54 min
Sep 5, 4:44 PM PDTSevere Thunderstorm WarningVEFSan Bernardino61 min
Sep 5, 4:50 PM PDTSevere Thunderstorm WarningVEFSan Bernardino55 min
Sep 5, 5:00 PM PDTSevere Thunderstorm WarningSGXSan Diego60 min
Sep 5, 5:45 PM PDTSevere Thunderstorm WarningVEFSan Bernardino60 min
Sep 5, 5:49 PM PDTSevere Thunderstorm WarningVEFSan Bernardino26 min
Sep 5, 6:04 PM PDTSevere Thunderstorm WarningPSRImperial25 min
Sep 12, 4:08 PM PDTSevere Thunderstorm WarningREVLassen, Plumas22 min
Dec 13, 12:45 AM PSTSevere Thunderstorm WarningLOXSan Luis Obispo, Santa Barbara60 min

By county

Every county with at least one alert. A county page lists each alert that covered it.

5 more counties

The busiest days

Days with the most alerts issued, by UTC date.

Nearby

Alerts in force nowTornadoes on recordThe radar archive20082010

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.