textproduct: San Joaquin Valley

KEY MESSAGES

1. Minor Heat Risk through Wednesday as temperatures remain around seasonal normal values.

2. Warmer temperatures dominate Thursday with a 30-50% chance of triple digits and a greater than 70% chance of Moderate Heat Risk throughout the Valley

DISCUSSION

In spite the calender showing we are in Fall, at least one more hot day is anticipated for 2026. Under the influence of high pressure moving warmer air from the south, Thursday temperatures will be 10-15 degrees above normal. Looking to the National Blend of Models (NBM), upper 90s are expected across the San Joaquin Valley with moderate confidence (50-60% chance) of exceeding 100 degree along the western side of the valley south of Highway 152. Across the entire forecast area, abnormally warm temperatures present a moderate risk of heat illness to those sensitive to heat. After Thursday, temperatures are expected to return back to seasonally average as the prevailing atmospheric pattern over central California turns benign.

Going into the start of next week, multiple weather models are in agreement that a trough of low pressure will move across the West Coast from the northwest. The extent of how far the trough digs southward into California is much less confident, thus providing a large spread of scenarios for the forecast area. Looking to the NBM for some clarity, a small but notable (5-10% chance) signal for at least a trace of rain exists between Sunday and Monday afternoon, with a higher (15-20%) chance for the Sierra Nevada and Mojave Desert of southeast Kern County. Instead of picking a winner to run with, updates to the next potential for rain will come as the weekend approaches.

Looking ahead to October, the Climate Prediction Center indicates growing confidence for above normal temperatures to start the month. The 6-10 Day Temperature Outlook (covering September 29-October 3) shows a slight leaning (40-50% chance) towards above normal temperatures, increasing to a 50-60% chance in the 8-14 Day Outlook valid October 1-7. No strong precipitation signal is apparent in either outlook, indicating no clear evidence for a wet, dry, or normal start to water year 2027.

AVIATION

VFR conditions will prevail for the next 24 hours.

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.