The start of the last official month of summer began Friday without scorching temperatures, muggy air, warm breezes or any of the other weather conditions that might seem normal for the Bay Area this late in the season.
Instead, the final countdown to summer began with calls for sweaters, an extra blanket for the bed and, for those in the northern part of the bay, an umbrella check.
What is winter?
“It’s pretty unusual,” said Dalton Behringer, a meteorologist with the National Weather Service. “It’s not totally out of the question that we could have a period like this in the summer, but in terms of climatology, it’s pretty rare.”
According to the weather service, temperatures are expected to exceed 21°C on Friday in the warmest areas of the region, but not more than 18°C in coastal areas.
According to Behringer, the arrival of such a winter system comes from the north. A deep low pressure system moves into the region from the Gulf of Alaska and brings with it very cold air into the upper parts of the atmosphere.
It could also bring up to a few hundredths of an inch of measurable rain to parts of Sonoma and Napa counties, as well as a chance of occasional drizzle in the East Bay and South Bay, according to the weather service.
The unusual August weather is the result of what Behringer calls a “pattern shift” in the weather system. Whether it symbolizes a change in what the region should expect in the final 30 days of the official summer season is a little harder to know, he said.
“It’s hard to say,” Behringer said. “Right now, this is just an isolated case. Certainly, it’s going our way because it’s going to prevent us from having offshore wind. That’s a good sign. It should also hopefully mitigate the fire season a little bit.”
The weather service says the cooling won’t last particularly long. Temperatures will begin to rise to seasonal norms by Sunday, and the hottest spots in the Bay Area are expected to reach at least 35 degrees by the middle of next week.
“By the end of next week, we’ll probably see temperatures drop back down a little bit toward seasonal norms,” Behringer said. “All things considered, it’s going to be pretty mild.”
