SAN FRANCISCO (KRON) -- A red flag warning has been issued for much of the San Francisco Bay Area as low humidity, strong winds and dry fuels create critical fire weather conditions, the National Weather Service announced Monday. The warning is in effect 11 a.m. Tuesday and runs through Thursday at 7 a.m. Offshore winds are expected to blow 20 to 30 mph with gusts up to 50 mph, weather officials said. The daytime relative humidity through the warning will be as low as 15 percent, with overnight recovery at 35 to 40 percent. High waves cause beach hazard in the Bay Area The interior Bay Area, including San Francisco, the San Francisco Peninsula and the Bay shoreline, are included in the red flag warning. The red flag warning also covers Santa Cruz County and higher elevations of the Central Coast. A red flag warning is in effect for portions of the San Francisco Bay Area 11 a.m. Tuesday through 7 a.m. Thursday. (Image: National Weather Service) Officials urge residents to have an emergency plan in case of wildfire and to exercise fire safety precautions. Critical fire weather conditions mean easier fire starts and the potential for rapid spread. On Sunday, PG&E announced that a dozen Northern California counties are “likely” to lose their power from Public Safety Power Shutoffs (PSPS) due to high winds and dry conditions. More than 10,000 customers across six Bay Area counties are estimated to have power cuts during the PSPS.