High pressure aloft with an inversion layer persisted since the last week of November. Low temperatures dipped into the mid 30s at times when the low clouds cleared in the Central Valley.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS HNX wrote it up.
High pressure aloft with an inversion layer persisted since the last week of November. Low temperatures dipped into the mid 30s at times when the low clouds cleared in the Central Valley. Otherwise, low temperatures were only slightly cooler when the low clouds, rather than fog, lingered. Patchy dense fog occurred at times during the first five days of the month in the San Joaquin Valley, but lifted to a stratus deck for the next few days. Dense fog was prevalent in the foothill areas, including the Grapevine, the Sierra Nevada foothills, and the coastal ranges at elevations between 1,000 feet and 2,500 feet from the 1st until the 9th.
Elsewhere, seasonably cool temperatures were recorded while dry conditions were present, such as in the mountains above 2,500 feet and the Kern County desert. Freezing overnight low temperatures were reported in the desert during the first several days of the month, which is common during December.
Fog and low stratus cloud cover continued over the San Joaquin Valley, as well as the lower Sierra Nevada foothills and coastal ranges up to around 2,500 feet for much of the second week of the month. However, dense fog became most prevalent in the San Joaquin Valley each night and morning from the 12th until the 15th. Most locations in the valley observed dense fog, even when they did not observe any clearing during the daytime on the 12th until the 15th. Enough moisture remained trapped in the Central Valley while the inversion layer served as a lid over the mountains and foothills due to the stagnant high pressure pattern in place.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Hanford, CA wrote its last area forecast discussion before the first event at Dec 2, 2:46 AM PST, 4 hours 14 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Hanford CA 246 AM PST Tue Dec 2 2025 .KEY MESSAGES... 1. Afternoon clearing has lead to fog development overnight into this morning across the San Joaquin Valley. 2. A dry disturbance will introduce increasing winds across the deserts and mountain peaks from Wednesday into Thursday. && .DISCUSSION... Tule Fog may make its return tonight into tomorrow morning due to the clearing of the stratus this afternoon and the lingering moisture in the atmosphere near the surface of the Valley. A Dense Fog Advisory has been issued for the majority of the Valley from 11 PM tonight through 11 AM tomorrow morning. Take caution while driving and slow down, especially on the highways and state routes as vehicles may be difficult to see in the fog. This fog potential is expected to return by Friday if the stratus that formed last week makes an appearance again. A system is then expected to move through the Great Basin Wednesday into Thursday, which may bring strong winds to the desert and mountain peaks during that time. This system is not expected to cause any precipitation, due to the fact that it will be moving out of western Canada and not offshore where it would otherwise pick up some marine air. The dry pattern is expected to continue through the weekend as a ridge builds in from the Pacific. && .AVIATION... IFR/LIFR visibilities are expected at all TAF sites until 20Z Tuesday. Between 12Z and 19Z Tuesday, VLIFR conditions have a 50% to 70% chance of occurring in dense fog. Conditions are expected to improve into MVFR/VFR conditions after 20Z and continue through at least 10Z-12Z Wednesday. && .AIR QUALITY ISSUES... On Tuesday December 2 2025, Fireplace/Wood Stove Burning Status is: No Burning Unless Registered in Fresno, Kern, Kings, Madera, Merced, and Tulare Counties. Burning Discouraged in Kern (Greater Frazier Park Area) and Sequoia National Park and Forest. && .CERTAINTY... The level of certainty for days 1 and 2 is medium. The level of certainty for days 3 through 7 is medium. Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.html for additional information and/or to provide feedback. && .HNX WATCHES/WARNINGS/ADVISORIES... Freeze Warning until 9 AM PST Tuesday for CAZ337>339. Dense Fog Advisory until 11 AM PST Tuesday for CAZ301>303- 305>307-309>316. && Aviation...Molina weather.gov/hanford
The national radar mosaic for the moment the first event began.
5 dense fog. Local standard time, as filed.
Dense fog with visibility to 500 feet in Visalia.
Dense fog with visibility at 200 feet or less at intersection of Highway 98 and Road |56.
Dense fog with visibility from 200 feet to zero at intersection of Highway 198 and 7th |Avenue.
CHP reports dense fog on the Grapevine portion of I-5.
Dense Fog of a quarter mile at the intersection of CA 198 and 2nd Avenue.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2025Every state in 2025This day in weather historyWarnings in California, December 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1302982, 1302985, 1302986, 1304886, 1304884.