textproduct: San Joaquin Valley

KEY MESSAGES

1. Warm conditions through the weekend with temperatures 5-10 degrees above normal.

2. Moderate fire risk with relative humidity below 20% in the foothills, Sierra Nevada and deserts.

3. High confidence in a pattern change early next week.

4. Temperatures well below average next week with moderate confidence of rain and high Sierra snow early Wednesday morning through Thursday.

PREV DISCUSSION

/issued 433 AM PDT Sat Oct 17 2026/ Another warm day is in store for the lower elevations on Saturday as we remain under a ridge of high pressure, including highs near 90 degrees in the San Joaquin Valley. Today's highs reached 90 degrees in some valley locations. Chances for maximum temperatures of 90 degrees or warmer on Saturday are at 55 to 65 percent for the Central Valley. Winds have generally decreased in the mountains and desert, while humidity has been improving in the mountain areas this evening.

Winds will further decrease on Saturday as pressure gradients relax as the upper- level low moves inland towards the Colorado River Valley.

For Sunday, above average temperatures continue, but with a minor decrease. Current probabilities for highs at or above 90 degrees in the San Joaquin Valley will be considerably lower than on Saturday, or at 15 to 25 percent. The ridge of high pressure weakens and gives way to an upper-level shortwave trough. This feature will eventually bring more noticeable cooling by Monday. Even more cooling and chances of precipitation enter the forecast for Tuesday and Wednesday. For the San Joaquin Valley we are looking at a 20 to 30 percent chance of rain with even better chances into Wednesday. There is moderate confidence that we will see a much cooler pattern, as highs struggle to exceed the lower 70s in the Valley for the latter part of next week. As of this writing, chances of a 70 degree reading or lower are at 50 to 60 percent for Wednesday until next Friday. Precipitation amounts of 0.10 inch ending Wednesday afternoon are at 35 to 45 percent for the San Joaquin Valley and of 0.50 inch or greater for the Sierra Nevada are at a similar percentage. As for the frozen precipitation, snow levels are at 8,000 feet on Tuesday and Wednesday with amounts of several inches, which can complicate travel along Tioga Pass/Road in Yosemite National Park.

AVIATION

VFR conditions will prevail for the next 24 hours. Winds will veer to the east at all terminals overnight while remaining light.

AIR QUALITY ISSUES

None.

CERTAINTY

The level of certainty for days 1 and 2 is high. 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

None.