California is baking under a dangerous, record-breaking October heat wave. At least 37 million people are under heat alerts as of Sunday, Oct. 4, with warnings covering nearly all of the state from the San Francisco Bay Area to the Mexican border, ABC News reports. The National Weather Service's extreme heat warning across Southern California will remain in effect until 8 p.m. Thursday, Oct. 8 — more than 150 hours, the longest October heat alert on record for the region.
Temperatures are running 15 to 27 degrees above normal for this time of year. Forecasters expect widespread highs in the 90s to low 100s again Sunday and Monday from the valleys to the coast, and more records could fall Sunday, according to the NWS. Unusually warm overnight lows are making things worse: in urban areas, nights will provide little to no relief, multiplying the health risk. In the Bay Area, heat advisories pushed San Franciscans to flock to Baker Beach near the Golden Gate Bridge on Saturday.
On Saturday, at least eight Southern California cities broke daily high-temperature records. Anaheim reached 105 degrees, breaking the old record of 103 set in 2014; Santa Ana hit 107, smashing the 2014 mark of 102; and San Diego reached 105, breaking a record dating to 1987. On Friday, downtown Los Angeles and Long Beach Airport both hit 103. Warm nights set records of their own: record-warm overnight lows were recorded in Anaheim (76), Santa Ana (72) and Newport Beach (70).
The heat is straining the power grid. With residents cranking up air conditioners, the California Independent System Operator, which manages the state's grid, issued a "Restricted Maintenance Operations" notice for 10 a.m. to 10 p.m. Monday and Tuesday, urging suppliers to avoid anything that could jeopardize generator or transmission availability, and asking customers to conserve power. A wildfire near Santa Clarita burned roughly 1,000 acres in under four hours on Saturday, a reminder of how quickly heat plus dry conditions can turn dangerous.
Relief is expected Thursday, with significant cooling by next weekend, according to the NWS. But forecasters warn the hot air will first expand east across the Great Basin, where highs are expected in the 80s and near 90s. Health officials urge people to drink plenty of fluids, stay in air conditioning, check on elderly neighbors, and never leave children or pets in cars — interiors can reach lethal temperatures in minutes.