Bay Area March Heat Wave Could Shatter Temperature Records Across Region

For the first time since the National Weather Service's San Francisco office began issuing heat advisories in 2006, it has issued one in March, as a sprawling high-pressure ridge drives temperatures across the Bay Area to levels not seen this early in the year in living memory. The advisory runs from Monday morning through Friday night, and forecasters say they may extend it into the weekend.

"It is going to be a marathon," the NWS office in San Francisco warned, a phrase that captures what forecasters say is not a brief spike but a prolonged stretch of 80- and 90-degree heat that could topple daily records, monthly records, and in some cities, all-time March highs. Temperatures are running as much as 30 degrees above normal for mid-March.

San José sits at the center of the most alarming forecasts. Meteorologists say the South Bay city has never recorded a 90-degree day in March in its entire climate history, which stretches back to the 1890s. The warmest March day on record there was 89 degrees, set in 2015. Now forecasters at KQED's weather sources say San José could hit 92 degrees on Tuesday, potentially shattering that record and logging three consecutive days in the 90s. The city could also break its record for the hottest back-to-back March days, set on Sunday in 2004 and Monday and Tuesday in 1914.

San José is not alone. NWS Bay Area meteorologist Dylan Flynn named San José, Santa Rosa, Redwood City, Livermore, and Salinas as cities that might set all-time high-temperature records for any day ever in March. "We expect a slew of daily records to be broken, and several monthly records are likely to go down as well," Flynn wrote in the local office's daily forecast discussion. Santa Rosa's current March record is 87 degrees, set in 1996. Livermore has held its March record since 1972. Tuesday's forecast has both cities approaching 90. San Francisco, Oakland, and Napa could also break their March temperature records, which date to 2004.

San Rafael has already fallen: the unseasonably warm weather broke a March daily heat record there before the week's peak has even arrived.

The NWS is tracking a heat risk escalation across the region. A Minor HeatRisk was in place through Sunday, upgrading to a Moderate HeatRisk from Sunday through Wednesday. ABC7 meteorologist Drew Tuma described a Major Heat Risk arriving Tuesday, when highs could run 20 to 30 degrees above average. The NWS predicts San Francisco will reach 73 degrees Sunday before climbing to a peak of 83 degrees on Wednesday. Inland communities will feel the worst of it: Concord, Napa, and Fairfield are expected to push into the high 70s to low 80s this weekend, then potentially reach the high 80s to low 90s by Wednesday.

Official record-keeping in San Francisco goes back more than 100 years, making this week's forecast all the more striking. It is also, health officials note, arriving before most bodies have adjusted to summer conditions. The NWS put it plainly: "This time of year, the body isn't used to dealing with this level of heat, so these highs are more impactful now than they would be in July." The agency's public guidance is direct: wear sunscreen, stay hydrated, stay out of the sun, and never leave anyone alone in a closed car.

Scientists say the pattern fits a trajectory shaped in part by human-caused climate change, which makes extreme heat events more frequent and more intense. Tens of millions of people across the desert Southwest and the California coast have been urged to curtail outdoor activities this week as the heat wave extends well beyond the Bay Area.