Extreme Heat Warnings and Heat Advisories cover much of California as October heat wave persists

The National Centers for Environmental Prediction (NCEP) said abnormally hot, potentially record-breaking temperatures would continue across Southern California and extend north toward the Bay Area and Central Valley during the week.

Local National Weather Service (NWS) forecast offices attributed the prolonged heat to strong high pressure over the western United States and anomalously high mid-level heights.

Weak upper-level disturbances were expected to provide little immediate relief, while offshore or weak onshore flow limited cooling from the Pacific in many coastal and valley areas.

Temperatures were forecast to remain 6–14°C (10–25°F) above average in parts of California through midweek. A stronger Pacific trough and increasing onshore flow were expected to bring more widespread cooling from late in the week into the weekend, although the timing and magnitude of the change varied by region.

NWS offices warned that prolonged daytime heat and limited overnight cooling would increase the risk of heat-related illness. Residents were advised to drink fluids, use air-conditioned spaces, reduce strenuous outdoor activity during the hottest hours, check on vulnerable people, and never leave children or pets in unattended vehicles.

NWS Los Angeles/Oxnard

NWS Los Angeles/Oxnard maintained an Extreme Heat Warning for the coasts and valleys of Los Angeles and Ventura counties, the Santa Clarita Valley, the Santa Monica Mountains, the southwestern and southeastern Santa Barbara County coasts, the county’s interior mountains, the Santa Ynez Mountains, the Cuyama Valley, and Catalina, Santa Barbara, Santa Cruz and Anacapa islands.

The product was issued at 11:04 PDT (18:04 UTC) on October 4 and remained valid until 20:00 PDT on October 8 (03:00 UTC on October 9).

Temperatures were forecast to reach 32–38°C (90–100°F) along the Los Angeles and Ventura County coasts and up to 41°C (106°F) in the valleys. Santa Barbara County coastal areas could reach 29°C (85°F), while the interior mountains and Cuyama Valley could reach 38°C (100°F).

The same office maintained a Heat Advisory for the San Luis Obispo County inland coast, mountains and valleys, the southern Salinas Valley, the Santa Barbara County inland central coast and the Santa Ynez Valley through 20:00 PDT on October 8.

A separate advisory for the San Luis Obispo County beaches and Santa Barbara County central coast beaches was scheduled from 10:00 PDT (17:00 UTC) on October 7 until 20:00 PDT on October 8. Temperatures of 27–35°C (80–95°F) were forecast in those coastal areas, while inland advisory areas could reach 39°C (103°F).

NWS San Diego

NWS San Diego continued an Extreme Heat Warning for Orange County coastal and inland areas, San Diego County coastal areas and valleys, the San Bernardino and Riverside County valleys, and the Santa Ana Mountains and foothills.

The warning update was issued at 03:19 PDT (10:19 UTC) on October 5 and remained in effect until 20:00 PDT on October 8 (03:00 UTC on October 9).

Forecast highs ranged from about 29–34°C (mid-80s to lower 90s°F) at the beaches to 35–41°C (mid-90s to 105°F) across higher coastal terrain, inland Orange County, the Inland Empire and San Diego County valleys.

Overnight lows were expected to remain near 20–24°C (upper 60s to mid-70s°F), with widespread Major to locally Extreme Heat Risk continuing across coastal areas and western valleys.

The office expected only slight coastal cooling through midweek. Valley and inland coastal temperatures were forecast to remain approximately 8–11°C (15–20°F) above average on October 7 before a more substantial cooling trend began on October 9.

NWS Las Vegas

NWS Las Vegas maintained an Extreme Heat Warning for elevations below 610 m (2 000 feet) in Death Valley National Park, including Furnace Creek, Stovepipe Wells and Shoshone.

The update was issued at 02:46 PDT (09:46 UTC) on October 5 and remained valid until 20:00 PDT on October 9 (03:00 UTC on October 10).

Highs near 43°C (110°F) and overnight lows around 29°C (85°F) were forecast, producing a Major to Extreme Heat Risk.

The office expected temperatures across its wider forecast area to remain 3–7°C (5–12°F) above average through October 9 before cooling began during the weekend.

NWS Hanford

NWS Hanford maintained a Heat Advisory for the San Joaquin Valley, Sierra Nevada foothills and Coastal West Hills.

The product was issued at 01:43 PDT (08:43 UTC) on October 5 and remained in effect until 23:00 PDT on October 7 (06:00 UTC on October 8).

Highs up to 39°C (102°F) were expected, with overnight lows of 21–24°C (70–75°F) in the warmest Sierra foothill thermal-belt locations.

The office forecast Moderate to Major Heat Risk and temperatures approximately 6–8°C (10–15°F) above average, with only minor short-term cooling before the ridge strengthened again.

NWS San Francisco

NWS San Francisco maintained a Heat Advisory for the East Bay and San Francisco Bay shoreline, the North Bay interior mountains and valleys, the Santa Clara Valley and eastern hills, the Santa Cruz Mountains, interior Monterey County and the Santa Lucia Range, most of San Benito County, and the southern Salinas Valley.

The product was issued at 23:01 PDT on October 4 (06:01 UTC on October 5) and remained in effect until 22:00 PDT on October 7 (05:00 UTC on October 8).

Maximum temperatures were forecast in the 35–39°C (mid-90s to low 100s°F) range.

Daytime highs were expected to remain approximately 8–14°C (15–25°F) above average and overnight lows approximately 6–11°C (10–20°F) above average, leaving limited nighttime relief across interior areas. The advisory for the immediate Pacific coastline had expired.

NWS Eureka

NWS Eureka expanded and extended a Heat Advisory across the northern and southern Mendocino interior and northern and southern Lake County.

The office issued the products at 21:04 PDT on October 4 (04:04 UTC on October 5), with the advisory remaining in effect until 22:00 PDT on October 7 (05:00 UTC on October 8).

Interior highs up to 41°C (105°F) and overnight temperatures of 16–21°C (60–69°F) were forecast, producing Moderate to locally High Heat Risk.

Near-record temperatures were possible across inland areas, while the immediate coast remained cooler under a shallow marine layer, low cloud and fog.

NWS Sacramento

NWS Sacramento maintained a Heat Advisory for the Sacramento and northern San Joaquin valleys, the Delta and Carquinez Strait, and adjacent foothills from Shasta County south through the Sacramento metropolitan area and into San Joaquin and Stanislaus counties.

The product was issued at 13:16 PDT (20:16 UTC) on October 4 and remained in effect until 22:00 PDT on October 7 (05:00 UTC on October 8).

Highs of 34–39°C (94–102°F) and lows of 18–22°C (mid-60s to low 70s°F) were forecast, with widespread Moderate Heat Risk and areas of Major Heat Risk.

The hottest conditions were expected from October 5 through 7, with some locations approaching daily temperature records before cooling began late in the week.

References

¹ WWA Summary for Extreme Heat Warning – NOAA/NWS – October 5, 2026

² Heat Advisory – NOAA/NWS – October 5, 2026