textproduct: San Joaquin Valley

KEY MESSAGES

1. A Heat Advisory has been issued for the San Joaquin Valley and Sierra Nevada Foothills through early next week. 20 to 60 percent chance for greater than 105 degrees in the Valley Friday and Saturday; 30 to 70 percent chance for Foothill areas to exceed 100 degrees.

2. Low RH values 15 to 20 percent will stretch across much of the San Joaquin Valley and Sierra Nevada with values 5 to 10 percent in the Mojave Desert. RH is expected to improve next week, but with widespread values still 20 to 25 percent.

3. 50 to 90 percent chance for temperatures to exceed 105 degrees for much of the Kern Desert over the weekend; 45 to 75 percent chance for Inyokern and Ridgecrest to exceed 110 degrees on Monday.

DISCUSSION

An area of high pressure is building over southern California today, starting a warming trend which will drive temperatures above season averages. There is a 20 to 60 percent chance for afternoon highs to exceed 105 degrees in the San Joaquin Valley on Friday and Saturday, with localized areas up to 70 percent. In addition, there is a 30 to 70 percent chance for highs to exceed 100 degrees in the Sierra Foothills, including Lake Isabella and Yosemite Valley. Minimum temperatures in the upper 60s for the valley areas, and the low to mid 70s in the foothill areas, will pair with the triple digit heat to cause widespread moderate heat risk for central California through the early part of next week. As such, a Heat Advisory has been issued for a large portion of the region, running from Friday morning through late Tuesday evening.

The warming temperatures bring lowered relative humidity, with widespread values 15 to 20 percent expected into the weekend; desert values will continue to be in the single digits. This will prolong dry conditions favorable for fire development, however with subsiding air aloft associated with the area of high pressure, winds will generally be light. The strongest winds will be in typical wind-prone areas such as the Mojave Desert Slopes, Lake Isabella, and Pacheco Pass, with the diurnal cycle being the main driver.

AVIATION

00Z Update:

VFR conditions will prevail for the next 24 hours across the Central California Interior.

AIR QUALITY ISSUES

ISSUED: 07/09/2025 14:29 EXPIRES: 07/10/2025 23:59

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

Heat Advisory from 11 AM Friday to 11 PM PDT Tuesday for CAZ300>322-324-325-332.