SAN DIEGO (FOX 5/KUSI) — San Diego Gas & Electric resumed public safety power shutoffs in stretches of San Diego's backcountry overnight into Tuesday as a Red Flag Warning for critical fire danger took hold. As of 9 a.m., nearly 900 customers had lost power out of the more than 54,000 who had received warnings from the utility company about potential service interruptions as a new round of Santa Ana winds set in over the region. Among the impacted areas are Alpine, Boulevard, Campo, Descanso, Julian, and the La Posta and Viejas reservations. One school district, the Mountain Empire Unified School District, has canceled classes Tuesday due to the shutoffs. Brush fire breaks out in Ramona amid Red Flag Warning A map of all of the current shutoffs and warnings can be found on SDG&E's website. According to the utility company, power may be restored as early as Wednesday evening, should fire risk subside. Public safety power shutoff map as of 7 a.m. (San Diego Gas & Electric) The shutoffs come as much of San Diego County's inland valley and mountain areas are under its second Red Flag Warning in just under two weeks. The warning for critical fire risk will remain in place through 6 p.m. Wedesday. Forecasters are attributing the protracted period of extreme fire danger in part to what has been the single driest start to the typical "rainy season" seen in the county's near 180-year weather history record, which has re-established severe drought conditions in the region. In the absence of any significant rainfall, the moisture in vegetation — much of it new growth following two back-to-back, record-setting winters — remains incredibly low, priming the environment for erratic fire behavior when strong winds set in and relative humidity dips. SDG&E and other public officials encourage San Diegans to exercise extreme caution with these conditions, including monitoring emergency notification systems and taking steps to reduce wildfire risk. According to the utility company, those impacted by the public safety power shutoffs can find Wi-Fi and other resources for phone and medical charging, among other things, at its Community Resource Centers. So far, two have been activated — in Boulevard and Descanso. This is a developing story. Check back for updates.