Large Scale Summary
- For near term conditions, the longwave pattern supports rain dates in the near term (May 26-29) focus into NORCAL coast and the Sierras from the Siskiyou
mountains in east Shasta Co south through the Lake Tahoe area to Fresno and Tulare Coís. End of May and month of June rain dates are: May 26-28, June 3-5, 8-15. - Look for greatest variation in speed of the westerlies at 30N and 40N. Most of this variation is due to interruptions in the westerlies at 30 to 43N, and in the tropical Pacific north of the 16N to 25N and longitudes 130-135W.
- Those functions that introduce increased variation in the westerlies occur at 30-40N for the most part as mentioned above. The increased variation tends to occasionally interrupt westerlies which occur along the usual development path in subtropical and midlatitude areas, including south to 25N.
- Near term rains focus on 26-29 May, and 3-5 June. We do not have July rain estimates yet from CFSDaily. What we are seeing for Arizona is higher than average rainfalls in the mountainous Mogollon Rim area of the upper Salt and Verde watersheds in early June and the 8-15th June from our FoxCFSDailyAI system.
- In summary, subtropical troughs and associated variations in speed of the westerlies can still develop near the end of late spring periods. This includes early to mid June, or more specifically, June 4 and 8-15.
- The favored locations of troughs continue to be mid-east Pacific around 150-135W and 170-155WÖwith a biasto maintain some occasional support for troughing to coastal California and possibly N Baja, and effect more rains into the near coastal areas of California in June.
- This upcoming summer to early fall season appears to be a potentially aggressive one for wildland fires in California due to thunderstorms (TSTMS) and recurrent periods of hot dry weather between the rain events.
- Looking ahead to early summer: mostly July there appears to be a maximum of rainfall SW-W Mexico to Baja, as well as north along the Sierra Madre Occidental,
and in the California Sierras from southcentral California to SOCAL during early to mid June. Weíll see this most likely from a cutoff low around 26-29 May, and again in 5 and 8-12 June. - Looking ahead to mid-July-August: While California is mostly warmer than average in July and August, Arizona appears to turn downward to near average in August, and possibly a little cooler than average in September.
NORCAL
- PRECIPITATION DATES MAY 26-28, MID JUNE THEN JULY-AUG: 8-12 JUNE. 1ñ8, 15 JULY. SHOWERS/TSTMS 14-30 AUG ACCOMPANIED IN AUG BY HOT SPELLS IN CALIFORNIA.
CENTRAL CALIFORNIA
- PRECIPITATION_DATES: Sierra SHOWERS/TSTMS 3-4, AND 8-12 JUNE IN N SIERRAS TO TAHOE-DONNER THEN SPREADING OCCASIONALLY SOUTH TO TULARE-FRESNO COíS IN THE SIERRAS..MOSTLY DRY WITH SOME HOT PERIODS: BEST CHANCES FOR RAINS: 26-29 MAY. TURNING BRIEFLY COOLER WITH RAINS ON 28 MAY. SHOWERS/TSTMS 3-5, 8-12 JUNE IN CENTRAL SIERRAS.
SOUTHERN CALIFORNIA
- PRECIPITATION DATES:25, 28-29 MAY. SOUTHERN CALIFORNIA SAN BDNO/LA CO MTNS/ TEHACHAPIíS 25, 28,29 MAY, 5, 8-12, JUNE
- SOUTHERN CALIFORNIA DESERTS: 28-29 MAY, 5,8-15 JUNE.PRECIPITATION DATES. VENTURA CO MOUNTAIN PRECIPITATION: RAIN SHOWERS/TSTMS 28,29 MAY, 4-5,8-12 JUNE.
MEDIUM TERM OUTLOOK: JUNE 25-JULY 30, 2026
NORCAL
- PRECIP DATES:25, 29-30 JUNE, 20-30 JULY includes MOUNTAINS. PRECIPITATION: MOSTLY NEAR AVERAGE IN EAST CALIF. BELOW IN WEST CALIF. MOUNTAIN RAIN: PRECIPITATION IS MAINLY SHOWERS/TSTMS WHEN OCCURING JUNE 8-15-JULY 1-10.
CENTRAL CALIFORNIA
- PRECIPITATION IS MAINLY SHOWERS/TSTMS WHEN IT OCCURS JUNE 22-JULY 22.PRECIPITATION JULY-AUGUST: Turning warmer than
average with TSTMS accompanying the precipitation.
SOUTHERN CALIFORNIA
- PRECIPITATION: NEAR AVERAGE. BEST CHANCES SHOWERS: POSIBLE EARLY BURST OF MONSOONAL RAINS IN MID JUNE, AND SOME ROBUST MONSOONAL BURSTS IN JULY AND AGAIN IN AUGUST. SEPTEMBER APPEARS UNUSUALLY MOIST DUE TO POSSIBLE TROPICAL CYCLONE EVENTS.
- SOUTHERN CALIFORNIA DESERTS PRECIPITATION: NEAR AVERAGE IN JUNE, ABOVE AVERAGE IN MID TO LATE JULY, AND MOSTLY ABOVE AVERAGE IN AUGUST. TURNING WARMER THAN AVERAGE IN JUNE AND JULY, WITH ABOVE AVERAGE RAINFALL FROM ACTIVE MONSOON RAINS, TSTMS, AND TROPICAL CYCLONE REMNANTS IN MID TO LATE JULY IN JULY. FOR WESTERN MEXICO, THE MONSOONAL INFLUENCE DECREASES AFTER LATE JUNE, CONTINUING ON THROUGH AUGUST.
Figures and Text: Alan Fox, Fox Weather, LLC
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