Heat, wind, dry air prompt North Bay red flag fire warning

An unwelcome meteorological hat trick - high temperature, low humidity and gusting winds - prompted the National Weather Service to issue a red flag warning Monday through Wednesday afternoon in the North Bay.

Temperatures expected in the low to mid-90s Tuesday and Wednesday, combined with dry air and offshore winds gusting up to 25 mph contributed to the warning, the service’s highest fire weather alert, meteorologist Roger Gass said Monday.

Heightening the risk are bone dry grass and brush that could make any fire cause for concern, he said.

The warning specifically applies to the North Bay hills, with the “highest threat” in the hills between Sonoma and Napa counties and around Mount St. Helena, but Gass said residents throughout the region should use “extreme caution” through Wednesday.

Within Sonoma County, the warning also covers the hills between the Santa Rosa Plain and Sonoma Valley.

Residents should avoid mowing or trimming dry grass, as well as driving over tall grass, he said. Anyone towing a camper, trailer or equipment should prevent the safety chain from dragging on the road and creating sparks, Gass said.

Any outdoor fire “will likely spread rapidly,” the warning said.

Dry northeast winds will begin posing a threat Monday night, blowing 10 to 20 mph with gusts reaching 25 mph.

Humidity will drop as low as 15 percent today and Wednesday afternoon, with “poor recovery overnight” at less than 30 percent humidity, the warning said. For a map and details go to weather.gov/mtr.

Santa Rosa is expected to be sunny with a daytime high of 92 degrees today and Wednesday, without significantly greater heat around the North Bay, Gass said. It will not be like the triple-?digit heat wave at the beginning of the month, he said.

Temperatures are expected to drop into the high 80s Thursday through Saturday, with a shift to cooler winds off the ocean late Thursday, Gass said.

The red flag warning also covers inland Mendocino County and much of Mendocino National Forest, as well as a broad swath of the Sacramento Valley and the western portion of the Sierra Nevada.

Point Reyes National Seashore officials posted a red flag alert for Monday through Wednesday afternoon, covering the 71,000-acre area on the Marin County coast.

The alert prohibits wood or charcoal fires on beaches and picnic areas, and smoking on park trails, voids all fire permits and closes Mount Vision Road to vehicle traffic, park spokesman John Dell’Osso said.

You can reach Staff Writer Guy Kovner at 707-521-5457 or guy.kovner@pressdemocrat.com. On Twitter @guykovner.