A Red Flag Warning has been issued for much of the Bay Area,
HEAT WAVE: Bay Area heat wave could bring 107-degree high temperatures
The warning goes into effect Saturday night at 9 p.m. and has been extended through Monday at 9 p.m. Winds are expected to be highest and fire danger most acute in the North Bay mountains and East Bay hills and valleys.
Winds are expected to gust "well over 30 miles per hour at times," says ABC7 News meteorologist Drew Tuma.
WATCH: Meteorologist Drew Tuma provides the full fire danger forecast
The reason these sorts of offshore winds are so dangerous during fire season is as the winds come over the hills and mountains, they speed up. The air also compresses itself as it comes down the mountain, explains Tuma, which heats up and dries out the atmosphere around it, creating prime fire conditions.
Due to the Red Flag Warning, the city of Concord will be closing its open space areas, including Lime Ridge Open Space and portions of Newhall Park. Lime Ridge parking lots at Treat Boulevard and Montecito Drive will also be closed.
The closures will take place from sundown on Saturday, Sept. 26 to 8 a.m. on Monday, Sept. 28.
VIDEO: East Bay residents bracing for triple-digit heat this weekend
As temperatures sizzle Sunday and Monday, bringing high winds and low humidity, fire crews are getting ready.
"Anytime we see Red Flag Fire warning, it raises our awareness, it raises our concerns," said Santa Rosa Assistant Fire Marshal Paul Lowenthal.
The warning comes only weeks after mass evacuations in Sonoma County, as the Walbridge Fire forced thousands from their homes.
Firefighters are urging everyone to be careful.
"Limit outdoor activities which could spark a wildfire locally," said Lowenthal.
RELATED: PG&E Power Outages: How to prepare for shut off
Dave Arcado isn't taking any chances, he's got a generator- ready to power his Oakmont Village Market in Santa Rosa, in case PG&E shuts the power off. Arcado hasn't received any alerts yet, but he lost power in early September during a planned power shutoff.
The stress has been terrible.
"We've had three years of fire danger, power outages now virus. It's draining," said Arcado.
MORE: Napa, Sonoma county residents 'likely' to lose power in PG&E power shutoff this weekend
Because of elevated fire conditions, PG&E has issued a PSPS Watch for much of Northern California, including hundreds in Napa County.
"PG&E may need to cut power this weekend to parts of Northern California due to an increased risk that its equipment could spark a wildfire," said company spokesperson Tamar Sarkissian.
On Saturday afternoon, Napa County officials issued an alert saying that PG&E has notified the county that a PSPS is likely to occur beginning at 4:00 p.m. on Sunday, Sept. 27.
Many of the areas of greatest concern have been afflicted with devastating wildfires since early August. While the CZU, LNU and SCU Lightning Complexes are all between 98% and 100% contained, there's concern that this weekend's weather could fan flames in those areas.
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