Extreme Heat Warnings cover Southern California as temperatures run 15 to 20 degrees above normal

Highs well into the 90s toward the coast and lower 100s in parts of the Central Valley are what the National Weather Service’s Weather Prediction Center describes for California this week, with temperatures running 15 to 20 degrees above normal. Extreme Heat Warnings cover portions of Southern California and the interior deserts, the center’s short-range discussion states, and the warnings remain in effect on Oct. 7.

Part of the same air mass is also moving northeast. The discussion has it spreading across the Great Basin into the northern Rockies, where highs in the middle and upper 80s, roughly 10 to 20 degrees above average, will challenge some daily records.

The Weather Prediction Center’s ridge forecast

The Weather Prediction Center’s short-range public discussion, issued at 3:55 p.m. Eastern on Oct. 5 and valid through Oct. 8, attributes the pattern to an anomalous upper-level ridge of high pressure over much of the West and into the northern Plains. The forecasters wrote that the outlook “has remained consistent with no change in hazardous heat messaging for the California Heat Wave,” and that temperatures “will run 15 to 20 degrees above normal.”

The discussion separates the warning tiers by region. Extreme Heat Warnings are in effect for portions of Southern California and the interior deserts, while Heat Advisories extend across the Central Valley and the Bay Area. Overnight lows in the mid to upper 70s in the Los Angeles and San Diego urban areas, the center notes, provide little relief during the heat wave.

Los Angeles and San Diego offices carry the warnings

The warnings themselves are issued by local forecast offices, not by the national center. The National Weather Service office in Los Angeles, based in Oxnard, lists Extreme Heat Warnings in effect through Thursday for the Los Angeles and Ventura County coast and valleys, the Santa Barbara County south coast and the mountains. Heat Advisories cover the rest of Santa Barbara County and San Luis Obispo County, with advisories on the Central Coast starting Wednesday morning. The office rates the heat risk as moderate to extreme and says a few daily records may be tied or broken each day, a forecast that keeps the warnings tied to the ridge instead of a single hot afternoon.

Records have already fallen. The Los Angeles office’s page notes Oct. 5 record highs, and an earlier Spectrum News report quoted the service saying the heat “actually exceeded expectations in and around the Downtown area where highs reached 102.” That report also had Woodland Hills at 103 degrees with 105 to 107 expected, and it named older adults, young children, outdoor workers and people with chronic conditions as the groups at greatest risk from a heat wave of this length, and it advised using cooling centers.

In San Diego County, the National Weather Service San Diego office also has an Extreme Heat Warning in effect. Its forecast describes offshore flow and strong high pressure bringing highs in the 70s and 80s in the mountains, 90s at the coast and 100s inland. For Wednesday it calls for mid 100s in the lower deserts, lower to mid 90s in the High Desert, mid 90s to lower 100s in the valleys and upper 80s to lower 90s at the coast.

Heat illness when nights stay in the 70s

Warm nights matter because the body gets little chance to shed heat before the next afternoon. The agency’s heat safety page says heat can be very taxing and can worsen existing health conditions, and it names young children, older adults, people with chronic conditions and pregnant women as the most vulnerable.

The heat illness guidance lists heavy sweating, weakness, cool, pale, clammy skin, a fast, weak pulse, muscle cramps, dizziness, nausea and fainting as signs of heat exhaustion. Heat stroke is the emergency form, marked by a body temperature above 103 degrees Fahrenheit, confusion, slurred speech and loss of consciousness, and the service says to call 911 or get the person to a hospital immediately.

The Centers for Disease Control and Prevention’s heat-health overview adds that anyone can suffer heat-related illness, and singles out children, adults 65 and older, pregnant women, people with asthma or heart disease, and outdoor workers and athletes for extra precautions.

Thursday, Oct. 8, is the next decision point for both offices. The Los Angeles office’s own text sets the end of the current warning at Thursday, Oct. 8, and the Weather Prediction Center’s discussion runs to the same day. The Oct. 1 Spectrum report had said warm conditions could persist into the following week, so whether the warnings are extended past Thursday is a call for the Oxnard and San Diego offices that no published product has yet made.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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