LARGE SCALE SUMMARY
- NORCAL rain dates in Northern and Central California and SOCAL are March 19-22, 24-25 and a few light showers March 30.
- Support for troughing continues in the central North Pacific from about 130-145W (mainly NE to N of Hawaii), and at 160W to near the Dateline N to NW of Hawaii. Arizona rains, from our FoxCFSDailyAI_B are
possible on Mar 25-26, and Apr 6, mainly north portions of Arizona. GFS suggests significant rains on March 17-18 and 21-23 per the GFS model. - Some of the rains in March include Southern California. As usually occurs in Spring, a few cutoff lows develop or move across SOCAL and Arizona.
- For forestry, the next wet spells appear for the following dates (rains and snows) March 18, 20-23, and 25-26 mainly snow with low snow levels.
NEAR TERM OUTLOOK — March 12 – April 12
- NORCAL precipitation dates in coastal valleys March 18-19, 20-25. Mild/dry periods with cool to near seasonally average temperatures. There is a seasonable warming from Mar 11 - April 10. Cool with occasional low snow levels.
- North Sierra precipitation March 20-23 and 24-26
- Central Sierra precipitation March 20-23, 24-27.
- Central California precipitation: Mar 14, 18,20-24, 24-27. Mild dry periods alternate with cold and (snow in mountains), only brief frosts/freezes mid to late March.
- Southern California - more rains occur in SOCAL about March 21-22, 23-24. Several nights may have frosts in the normally colder valleys, on nights in which clearings occur for a time overnights/early mornings between fronts/rain events, e.g. Mar 18-19. Dry/warm (Santa Ana) type events March 18-19.
- Southern California Deserts - Colder than average during rainy periods. Rainfall amounts below average. Rain dates in SOCAL Deserts: Mar 12-13-showers 14th. Rains/showers 20-22, 23-24. Rain sparse or unlikely in April.
MEDIUM TERM OUTLOOK — April 12 - May 12
- Northern California: Near average precipitation with temperatures trending above average about first week of April and again during last week of April. Mid April rains are focused in central California. Rainfall may still average near normal in April for Central California, based on the drizzle occurring over several days. Well below average during mid April, otherwise warmer than average during warmest periods (first week of April and about the last week. About average number of frosts/freezes for April in the coastal valleys, depending on depth of the marine layer during 18-20th. Watch for onshore flow and deep marine layer conditions extending thru the Delta to Sacramento-Stockton-north San Joaquin Valley. Morning drizzle will be most likely Stockton to Sacramento. Most of frost if any is suggested for the period April 21-22 , followed by days having much warmer than average through end of April and beginning of May.
- Southern California: Near average precipitation with temperatures trending above average about first week of April, and again during last week of April. SOCAL will most likely receive low clouds (stratocumulus) and cool conditions, with morning to midday drizzle during the mid April period. Cooler than average during mid April, otherwise shifting quickly to very warm or hot conditions (away from marine influence) during warmest periods (first week of April and late April - start of May. About average number of frosts/freezes for April. Most of the frosts are suggested for the period April 22-23 if any, followed by days with much warmer than average through beginning of May.
LONG TERM OUTLOOK — May 12-June 30
- Northern California: Near average precipitation, highest precipitation anomaly will be at the North Coast Mendocino Co north from coastal drizzle and light rains from weak end-of-season cold fronts in early May. Note that we dry out quickly after the first week or so of May. After about 12 May, temperatures turn to well above average Sacramento Valley, and well above average in central to southern Sierras (warm nights on slopes with inversion conditions). Frost conditions are not an issue this season 2025 after about 10 May. Watch for frosts in the Mendocino Co valleys (viticulture areas) and possibly southern Lake Co during the first week of May, but unlikely when clearing/drying occurs after about 10 May. For valleys and mountains of Northern California, turning hotter and drier than average during late spring and first month of summer (June).
- Southern California: Near average precipitation with near average temperature. Below average number of frosts/freezes in valleys of SOCAL outside the marine influence zone, especially north part, i.e. valleys of San Luis Obispo, Santa Barbara, Ventura Counties during the first week to 10 days of May followed by dry and hot conditions starting to develop in mid to late May. Please note that well above normal temperatures are suggested in the NCEP/CPC guidance for June suggest heat wave conditions in the Sierra Nevada foothills and west slope areas from El Dorado Co south. This is important because with dry conditions in May and June, this may set the stage for an early start to fire season. For the valleys of Southern California: turning warmer and drier than average during the late spring and the first month of early summer (June). We note from the NCEP monthly guidance that extreme heat is a possibility in June for inland SOCAL citrus and avocado regions. There is risk of highs reaching to near 110 in the Ramona-Temecula areas and a little over 100 in Fallbrook during mid to late June.
Figures: Alan Fox, Text: Alan Fox, Fox Weather, LLC.
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