National Weather ServiceCaliforniaDense Fog AdvisoryArchive to October 1, 2026
Dense Fog Advisories in California
The National Weather Service issued 188 dense fog advisories for California in 2025 and 107 a year on average in 2008-2025; in 2021-2025 it had the 2nd most of any state. 2026 through September: 67, 24% above the average of 54 for those months in 2008-2025. San Diego County Coastal Areas was covered most often (291 times since 2008).
How many dense fog advisories does California get?
Every dense fog advisory that covered part of California. 2026 is an outline: the year is not over.
The numbers
| Year | Count |
|---|---|
| 2026 (through September) | 67 |
| 2025 | 188 |
| 2024 | 160 |
| 2023 | 124 |
| 2022 | 118 |
| 2021 | 141 |
| 2020 | 117 |
| 2019 | 79 |
| 2018 | 92 |
| 2017 | 75 |
| 2016 | 83 |
| 2015 | 88 |
| 2014 | 89 |
| 2013 | 86 |
| 2012 | 93 |
| 2011 | 126 |
| 2010 | 91 |
| 2009 | 68 |
| 2008 | 102 |
Source: Iowa Environmental Mesonet archive of National Weather Service watches, warnings and advisories (VTEC); National Weather Service. Data as of October 1, 2026.
When in the year does California get them?
Sum of 2008-2025; the busiest month is labelled.
Source: Iowa Environmental Mesonet archive of National Weather Service watches, warnings and advisories (VTEC); National Weather Service. Data as of October 1, 2026.
Where in California?
| County or forecast zone | Since 2008 | Since 2023 | Last issued |
|---|---|---|---|
| San Diego County Coastal Areas | 291 | 52 | January 21, 2026 |
| Northern San Joaquin Valley | 253 | 71 | February 26, 2026 |
| Southern Sacramento Valley | 245 | 66 | February 26, 2026 |
| East-Central San Joaquin Valley | 212 | 0 | February 1, 2019 |
| Southeastern San Joaquin Valley | 212 | 0 | February 1, 2019 |
| Southwestern San Joaquin Valley | 211 | 0 | January 30, 2019 |
| West-Central San Joaquin Valley | 204 | 0 | January 30, 2019 |
| Santa Barbara County Central Coast | 196 | 0 | March 26, 2022 |
| Carquinez Strait and Delta | 195 | 54 | February 5, 2026 |
| Hanford - Corcoran - Lemoore | 193 | 137 | February 28, 2026 |
| Caruthers - San Joaquin - Selma | 186 | 131 | February 28, 2026 |
| San Luis Obispo County Central Coast | 184 | 0 | March 24, 2022 |
The NWS issues these products for counties or forecast zones; a zone can be part of a county or a mountain range.
Source: Iowa Environmental Mesonet archive of National Weather Service watches, warnings and advisories (VTEC); National Weather Service. Data as of October 1, 2026.
What is a dense fog advisory?
A dense fog advisory means fog will cut visibility to a quarter mile or less over a wide area. An advisory is issued for a hazard less serious than a warning that can still cause inconvenience or danger if people are not careful. The national record · Every warning type in California.