Defining a single “late winter” period for California is challenging due to the state’s immense north-to-south span and dramatic changes in elevation. The state is a mosaic of microclimates, where coastal areas, desert valleys, and alpine mountain ranges experience winter’s end in fundamentally different ways. California’s late winter timing is deeply influenced by whether a location is moderated by the Pacific Ocean or sitting atop a major mountain chain. To accurately determine when late winter occurs, one must break down the answer geographically, as the end of the cold season can span from mid-February to late May depending on the specific locale.
Defining the Late Winter Period in California
Late winter in California is the period immediately following the coldest meteorological months of December, January, and February. While astronomical winter ends around the spring equinox (March 20th or 21st), the state’s late winter weather window generally runs from mid-February through the final days of March. This is when California receives the last of its major precipitation events, often delivered by atmospheric rivers that contribute significantly to the water supply. This time is characterized by a final push of cold storms, which is crucial for maximizing the deep snowpack in high elevations.
Coastal and Southern California Timing
The late winter period is shortest and mildest in coastal and Southern California regions, including Los Angeles, San Diego, and the San Francisco Bay Area. These regions experience a Mediterranean-like climate and often see a rapid transition to spring conditions beginning in mid-February. Average high temperatures in mild areas like Los Angeles often hover around 68 to 72 degrees Fahrenheit during the winter months, offering many sunny, spring-like days.
This period marks the effective end of the rainy season, which traditionally runs from December through March. Significant precipitation becomes less frequent as March approaches. By the middle of March, many lower elevations begin to show the earliest signs of the wildflower season, a biological marker of the end of winter. This early shift is due to the moderating influence of the Pacific Ocean, which prevents the extreme cold experienced elsewhere in the state. The transition is often so swift that a traditional, prolonged spring is bypassed in favor of a direct move toward warmer, drier conditions.
Mountain and Northern California Timing
For the high-elevation areas of California, such as the Sierra Nevada and Cascades, late winter is a prolonged and intense period that often extends into April, and sometimes even May. The timing is determined by the snowpack, which provides about 30 percent of the state’s water supply and typically reaches its maximum accumulation during this late winter window. January, February, and March are historically the largest snow-producing months in the Sierra Nevada.
Continued cold storms are necessary to build the “frozen reservoir,” with heavy snowfalls occurring frequently above 7,000 feet. Late winter is synonymous with the peak ski season and the highest risk for avalanches. Safety precautions for winter travel, including chain requirements on mountain passes, remain fully in effect, sometimes lasting until Memorial Day weekend or later. The official end of the winter season in the mountains is often defined by the opening of high-altitude roads, like Tioga Pass, which can remain snowbound until late May or June in heavy snow years.
Central Valley and Desert Timing
Late winter presents a distinct experience in the Central Valley, stretching from Sacramento to Bakersfield, and in the state’s desert regions.
Central Valley
In the Central Valley, late winter is characterized by the dissipation of the notorious Tule Fog. This thick radiation fog can settle for days from late fall through March. As the sun angle strengthens and temperatures rise in late February and early March, the atmospheric inversion layer trapping the fog begins to break down more consistently. The disappearance of the Tule Fog signals a rapid shift away from the damp, chilly conditions. These conditions require a period of “winter chill” for the region’s fruit and nut orchards to flourish. The Central Valley often jumps quickly into warm, dry conditions, essentially bypassing a mild spring season entirely.
Desert Regions
In the low-lying deserts like the Coachella Valley, late winter is arguably the most pleasant time of year, with average high temperatures in the mid-70s before the summer heat arrives. This transitional period is defined not by lingering cold, but by ideal weather that precedes the extreme heat. It offers a brief, comfortable window before the season shifts to scorching conditions.