MONTEREY — The cool and brisk fall weather the Bay Area has seen over the past week isn’t set to last for long, as forecasters predict a slow warming and drying trend that could pose a real danger to firefighters battling blazes across the state.

National Weather Service meteorologist David King said Sunday was the beginning of a “pattern change” in weather as a high pressure system starts to grow along the eastern Pacific Ocean and right along the coastline.

However, a gradual increase in temperatures expected this week won’t be like the sweltering heat waves that hit the state this summer, he added. Instead, it will get progressively warmer throughout the week, starting with temperatures in the mid-60s to low-80s.

As the high pressure grows by mid-week into Wednesday, King said, inland regions in the Bay Area will see highs from the lower 80s to mid-90s, with the hottest temperatures expected Thursday and Friday in the valleys.

“It’s not going to be any kind of extreme heat even but temperatures are going to warm up,” King said. “For the past four or five days we’ve had this wonderful marine layer and fog. But unfortunately the marine layer is going to erode away as offshore winds develop.”

It’s the offshore winds that keep firefighters nervous as they tune into weather updates hoping for help from mother nature in fighting blazes that have so far burned more than 4 million acres in California. The Glass Fire, burning in Napa and Sonoma counties, reached 90% containment as of Sunday morning. That blaze has consumed some 67,000 acres and destroyed more than 600 single-family homes; it still threatened about 2,000 structures as of Sunday, fire officials said.

Wind speeds at higher elevations were fairly low on Sunday, but even slow winds could dry out any moisture that the landscape retained from humid conditions last week.

“It’s going to elevate fire concerns later on this week as models are showing winds are going to increase in the Wednesday to Friday time range,” Kind said. “At the end of the week we’ll have stronger offshore winds.”

Bay City News Service contributed to this report.