Wind, heat and low humidity have prompted the National Weather Service to issue a Red Flag warning for the Santa Cruz Mountains from 10 a.m. Tuesday to 8 a.m. Wednesday. The Red Flag warning is also in effect for the North Bay mountains and East Bay hills from 10 p.m. Monday to 8 a.m. Wednesday.
"A Red Flag Warning means that critical fire weather conditions are either occurring now or will shortly. A combination of strong winds, low relative humidity and warm temperatures can contribute to extreme fire behavior," the weather service said. "Any fires that develop will likely spread rapidly. Outdoor burning is not recommended," the weather service noted in a written announcement.
"After low pressure drops over the Intermountain West beginning late Monday, winds will shift to the north-northeast and becoming gusty in the North and East Bay Hills by Monday evening and in the Santa Cruz Mountains by Tuesday morning. Locally gusty offshore winds will then continue at times in the North and East Bay Hills and Santa Cruz Mountains through Wednesday morning."
In conjunction with these locally gusty offshore winds, overnight humidity is expected to be poor due to the absence of a marine layer. Humidity will drop into the teens during the daytime hours, the weather service said.
Sustained north to northeast winds at 15 to 25 mph with gusts 30 to 45 mph above 1,000 feet are expected. Local gusts at isolated peaks and ridgetops might approach 50 mph. The strongest winds are expected late Monday night and Tuesday morning. The interior, higher terrain of the North Bay mountains and the East Bay hills face the highest threat, the weather service noted.
The weather service announced the warning at 2:32 p.m. on Sunday in the midst of a heat wave that is causing temperatures to top more than 100 degrees throughout the region. Temperatures hit 107 degrees at the weather service's Los Altos monitoring station on Sunday afternoon. The warning upgraded a "Fire Weather Watch" made earlier in the day.