Forecasters have upgraded a fire weather watch issued earlier this week to a red flag warning for strong winds, low humidity levels and increased fire danger through Friday evening.
The warning area as of Thursday night covered the valleys of Riverside and San Bernardino counties, and the mountains on the south side of the San Gorgonio Pass, including the San Jacinto ranger district of the San Bernardino National Forest.
"Surface high pressure building over the Great Basin will bring areas of strong gusty winds through Friday, especially through and below passes and canyons," the National Weather Service advised Thursday afternoon.
"These winds will combine with very low humidity to bring elevated fire weather conditions for the mountains south of San Bernardino County and the inland valleys. Conditions will gradually improve Friday night as winds diminish."
Daytime highs for Friday in Banning and Beaumont are expected in the high 60s, according to the Weather Service.
East winds of 15 to 30 miles per hour are expected in some areas Friday, with gusts 35 to 45 mph, and minimum humidities 10 to 15 percent.
A red flag warning means "critical fire weather conditions" are occurring or imminent. A combination of strong winds, low humidity levels, and warm temps can contribute to extreme fire behavior.
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