Temperatures that scorched part of the Bay Area on Tuesday and Wednesday were falling by at least double digits Thursday, in large part because of winds created by a pocket of low pressure, high in the atmosphere, that kept a two-day heat-up from gaining any traction.

Yet the fire danger figures to be as significant as it has been at any time this year, according to the National Weather Service and fire officials.

“That upper-level low across the Pacific Northwest is causing a pressure gradient across the region,” NWS meteorologist Dial Hoang said Thursday. “That’s causing the winds to pick up in their intensity, especially across the coastal region and some of the passes.”

Those winds are expected to blow steadily with gusts of between 25 and 40 mph, according to Hoang. He added that there is still onshore flow but that elements associated with offshore winds coming from the north also are present.

As a result, the weather service noted what it called a “near-critical fire weather threat” into Saturday as humidity is expected to drop to 15-25%. The threat is most dangerous in the East Bay Hills, the eastern Santa Clara Hills and the Gabilan Range of San Benito and Monterey counties, according to the weather service.

Hoang said the Altamont Pass also is in the danger zone.

Before that weather settled in, fire crews were forced to tackle a wildfire in Antioch that grew to 290 acres. Crews stopped the forward progress Wednesday night, and had the fire 100% contained by midday Thursday, according to fire officials.

That fire brought an air quality advisory on Wednesday night for areas in the East Bay near the fire. That advisory was not in effect Thursday and measurements by the Bay Area Air Quality District showed good air quality throughout the region.

PG&E responded to the weather threat by announcing a public safety power shut-off. At 12:30 p.m. Thursday, about 500 customers in Contra Costa County had been affected by the PSPS, along with about 640 customers in Alameda County and 50 customers in Santa Clara County.

The utility said a PSPS also was likely in San Joaquin, Stanislaus, Merced and San Benito counties. Approximately 11,500 customers were in the service areas most likely to be affected, according to PG&E.

“Because the winds are so strong, the interior areas are going to get really dry,” Hoang said. “That’s where the elevated fire weather is coming from.”

The gusty winds are expected to continue at least into Saturday and probably through it, Hoang said. Their intensity is expected to drop significantly by Sunday, along with some of the immediate fire danger.

As for the temperatures, they will peak no higher than the low 80s in the hottest places on Thursday, according to the weather service. Most inland places won’t escape the 70s, and coastal temperatures are expected to remain in the 60s. Hoang said they will stay there until at least the middle part of next week.