Rare Red Flag Warning Issued As Dry Bay Area Heat Elevates Fire Danger

SAN FRANCISCO, CA — The fire threat will ramp up across the Bay Area on Wednesday, presenting critical fire concerns for interior areas of the North Bay and prompting a rare Red Flag Warning, according to the National Weather Service.

The warning will be in place for the interior mountains of the North Bay between Tuesday night and Wednesday evening, with the eastern reaches of Napa County at highest risk. In that area, forecasters expect gusty north winds ranging from 30-40 mph as afternoon humidity struggles to hit 20 percent.

The Red Flag Warning is the first issued in nearly two years from the National Weather Service's Bay Area office, but forecasters are optimistic that the weather conditions won't be as severe as those that have led to major wildfires in the North Bay, like in the fall of 2017.

"[We] want to emphasize that this is a lower-end Red Flag Warning and will not be on par with past conditions that led [to] notable North Bay fires," NWS Bay Area forecasters wrote Tuesday. "Regardless, please avoid outdoor activities that could cause sparks."

Forecasters expect the entire Bay Area will run hot, dry and hazy Wednesday afternoon as even San Francisco looks to top 80 degrees. Firefighters were already contending with blazes elsewhere in the Bay Area on Tuesday, including one in Contra Costa County that shut down a stretch of Highway 4.

The Bay Area will also be under a Spare the Air alert Wednesday while contending with more wildfire smoke and heat.

"With [an] increase in northerly winds, the Bay Area and Central Coast will unfortunately see an influx of near-surface smoke tonight into tomorrow from fires burning in the northwest portion of the state," forecasters warned Tuesday. "Tomorrow is also anticipated to be the warmest day this week with highs in the interior in the mid-to-upper 90s while the coast will be in the upper 70 to upper 80s. Warm temperatures plus increased smoke/haze may mean folks should rethink outdoor plans tomorrow if possible."

Fortunately, the heat should break after Wednesday, allowing much cooler temperatures to take hold across Northern California. Temperatures are expected to tumble several degrees below normal on Friday and Saturday, and the North Bay even has a chance of rain showers.