Dense Fog Advisories in California
2,198 dense fog advisories since 1986. 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 dense fog advisories reaches back to 2005.
Dense Fog Advisories by county
Each county as a circle sized by its count since 1986. Tap one for its archive.
- Dense Fog Advisories
- 2,198
- Busiest year
- 2025188 dense fog advisories
- Average year
- 100over 22 years on file
Over time
By year
Before late 2005 the archive holds only tornado, severe thunderstorm, flash flood and marine warnings, and from 1997 SPC's watches, so the jump that year is the archive widening, not the weather.
By month of the year
By county
Every county with at least one alert. A county page lists each alert that covered it.
- San Diego County365
- Fresno County206
- Tulare County199
- Kings County195
- Kern County179
- Marin County174
- Sonoma County174
- Madera County164
- Merced County164
- Orange County160
- Napa County159
- Mariposa County125
- Alameda County122
- Contra Costa County122
- Monterey County118
- San Mateo County114
- Los Angeles County108
- Santa Barbara County104
- Santa Clara County93
- Santa Cruz County93
- San Bernardino County91
- San Benito County88
- Riverside County86
- San Luis Obispo County81
- City and County of San Francisco80
- Ventura County68
- Siskiyou County37
- Imperial County35
- Humboldt County33
- Del Norte County25
- Modoc County14
- Plumas County9
- Sierra County9
- Lassen County9
- Mendocino County8
- Alpine County2
- El Dorado County2
- Nevada County2
- Placer County2
- Inyo County2
1 more counties
The latest dense fog advisories
The most recent on file, newest first.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 3, 2:02 AM PDT | Dense Fog Advisory | MTR | Monterey, San Mateo, Santa Cruz | 7 hr |
| Oct 2, 5:38 AM PDT | Dense Fog Advisory | LOX | Los Angeles, San Luis Obispo, Santa Barbara, Ventura | 4 hr |
| Sep 29, 7:47 AM PDT | Dense Fog Advisory | MTR | Monterey, San Benito | 73 min |
| Aug 29, 5:04 AM PDT | Dense Fog Advisory | MTR | Marin, Napa, Sonoma | 4 hr |
| Jun 1, 9:10 PM PDT | Dense Fog Advisory | MTR | Monterey | 9 hr |
| Jun 1, 5:23 AM PDT | Dense Fog Advisory | MTR | Monterey | 4 hr |
| Mar 29, 5:27 AM PDT | Dense Fog Advisory | LOX | Los Angeles, San Luis Obispo, Santa Barbara, Ventura | 6 hr |
| Mar 28, 7:45 AM PDT | Dense Fog Advisory | LOX | San Luis Obispo, Santa Barbara | 2 hr |
| Mar 27, 5:11 AM PDT | Dense Fog Advisory | LOX | Los Angeles, Santa Barbara, Ventura | 5 hr |
| Mar 18, 5:19 AM PDT | Dense Fog Advisory | EKA | Del Norte, Humboldt, Mendocino | 3 hr |
| Feb 28, 11:57 PM PST | Dense Fog Advisory | LOX | San Luis Obispo, Santa Barbara | 10 hr |
| Feb 27, 12:57 PM PST | Dense Fog Advisory | HNX | Fresno, Kern, Kings, Tulare | 19 hr |
Nearby
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.