This post summarizes a recent cold snap in California that prompted an Extreme Cold Watch. It offers expert context on why it happened, who is most at risk, and what communities, farmers, and emergency managers should consider as ENSO conditions evolve.
Drawing on meteorological observations and decades of experience in weather impacts, I explain the mechanisms behind the freeze and how local geography amplified conditions. Practical actions to reduce harm to people, animals, and crops are also discussed.
What happened: a shallow, persistent cold event
The National Weather Service in San Francisco identified clear skies, long winter nights, and a light offshore flow as the ingredients that allowed a shallow “cold lid” to form near the surface the night of Jan. 8 into the morning of Jan. 9. This stable atmospheric layer trapped colder air in valleys and low-lying areas while coastal zones were moderated by the ocean and downslope winds.
Meteorology and local effects
Strong winds accompanied the cold, especially through the mountains, valleys, and foothills of Los Angeles, Santa Barbara, and Ventura counties. Santa Ana winds were forecast to continue through the weekend.
Forecasters expected many spots along the Central Coast, the Bay Area, and northern interior to reach the upper 20s Fahrenheit on the coldest nights. In practical terms, this means temperatures that might be routine elsewhere can become dangerous here because some California infrastructure and communities are not designed for sustained subfreezing conditions.
Pipes, water delivery systems, vulnerable housing, and many crops can be affected well above traditional “arctic” thresholds.
Who is vulnerable and immediate risks
Even modest winter lows present outsized risk in California. Unhoused populations, elderly residents, pets, livestock, and sensitive crops are at highest immediate risk.
Below-freezing nights increase hypothermia risk, can damage exposed irrigation equipment, and harm susceptible fruit and vegetable crops that lack frost protection.
Historical perspective and perspective on severity
California’s all-time record low remains an extreme outlier at -45°F in Boca, near Truckee on the Nevada border. Historical coldest-city lows include Los Angeles 27°F (1949), San Diego 25°F (1913), San Francisco 27°F (1932), Sacramento 17°F (1932), and San Jose 18°F (1894).
The recent event, with targeted upper-20s readings in places, is notable more for impact than for record-breaking numbers.
ENSO forecast and seasonal outlook
Looking beyond the immediate event, the National Weather Service predicts a transition from La Niña to a neutral ENSO phase between January and March. El Niño is likely later in 2026.
For planners this matters: La Niña tends to bring cooler, snowier conditions to the Pacific Northwest and drier-than-normal weather to much of the southern U.S. An emerging El Niño can shift storm tracks and precipitation patterns the following year.
What to do now: practical preparedness
From my 30 years of experience in weather impacts, targeted preparedness reduces casualties and economic loss.
Here are immediate actions for residents, municipalities and growers:
Here is the source article for this story: Why is it so cold? What to know about the ‘Extreme Cold’ in California