A prolonged heat wave continued across California over the weekend, breaking daily high-temperature records at multiple locations, while hot and dry conditions and wildfire smoke added to health and fire risks across parts of the state, according to the U.S. National Weather Service (NWS) and state authorities.
A preliminary report from the NWS San Diego office said eight daily high-temperature records were broken and one was tied on Oct. 3 across Orange, San Diego and Riverside counties.
Santa Ana in Orange County reached 41.7 degrees Celsius, about 2.8 degrees above the previous record for Oct. 3 set in 2014, while Vista in San Diego County reached 42.2 degrees, according to the report.
San Diego International Airport reached 40.6 degrees, breaking a daily record that had stood since 1987. The temperature was about 16.1 degrees above normal for the date, according to an NWS climate report.
Farther north, Napa Airport reached 35.6 degrees, breaking its previous Oct. 3 record of 34.4 degrees, according to the NWS San Francisco Bay Area office. In northern Nevada, Winnemucca Airport reached 32.2 degrees, breaking its previous daily record set in 2024, according to the NWS Elko office.
The NWS Los Angeles/Oxnard office described the episode as a major and long-lasting heat wave and said unusually high temperatures were expected to persist through the coming week.
More than 34 million Californians were under heat warnings or advisories. Extreme Heat Warnings remained in effect through Thursday evening in parts of Southern California, including San Diego and the coasts and valleys of Los Angeles and Ventura counties and parts of Santa Barbara County.
The California Department of Forestry and Fire Protection (CAL FIRE) website listed several active incidents Sunday, including the Bouquet Fire in Los Angeles County, which had burned 1,048 acres and was 40 percent contained, and the Dome Fire in Mariposa County, which had burned 6,826 acres and was 40 percent contained.
Across California, CAL FIRE reported 5,701 wildfires and 328,950 acres burned in 2026, with three fatalities and 157 structures destroyed. The figures are preliminary and subject to frequent updates.
Smoke from active wildfires adds another health concern. Fine particulate matter, known as PM2.5, can penetrate deep into the lungs and is particularly harmful to children, older adults and people with heart or lung conditions, according to California health authorities.
AirNow forecasts showed air quality reaching levels considered unhealthy for sensitive groups in several California communities on Sunday, with ozone identified as the main pollutant in a number of areas.
Health officials advise residents to limit strenuous outdoor activity during periods of extreme heat or poor air quality, keep windows and doors closed when smoke is present, use air conditioning on recirculate and seek a cooler, cleaner-air location when necessary.