Bay Area temps set to cool down this weekend

Forecast calls for end of record-setting heat wave that kicked off the month of February

The record-setting heat wave that kicked off February finally will end this weekend, Bay Area experts say.

“Typically in February, we would be getting rain and cooler temperatures, but this winter, and especially this month have been abnormally warm,” said Brian Mejia, a meteorologist with the National Weather Service.

The latest streak of high temperatures is caused by a high-pressure ridge currently over the eastern Pacific, which is driving weather over the Bay Area and the Central Coast in California, Mejia said.

This high-pressure ridge will weaken over the weekend and temperatures should drop by Monday.

“Even this weekend, we’ll see things trend cooler,” Mejia said.

Every day this month, there have been records broken or at least tied for locations around the Bay Area. Both San Jose and Half Moon Bay, for example, have set or met records in the past week. On Thursday, Gilroy’s temperature spiked to a balmy 82 degrees, breaking the previous record of 78 degrees from 1963.

Jan Null, adjunct professor of meteorology at San Jose State, has been keeping track of precipitation.

The last time the region saw rain was Jan. 25.

“So, we are at 15 days without rain,” Null said. It is by no means a record — 43 days is the longest stretch without rain recorded in winter at the San Francisco climate station. The longest dry spell outside of winter clocked in at 194 days.

According to Null, these dry spells occur because the atmosphere is trying to reach equilibrium.

“It’s just like if you have a heater on in one room of your house — gradually, all the other rooms around it will equalize to the same temperature,” Null said. “The atmosphere is the same way.”

As heat travels from the equator to the poles, waves of high and low pressure wash over the Bay Area. When the transfer of heat back and forth between the equator and the poles reaches an equilibrium, Null said, “Things get stuck.”

December was dry, while January’s rainfall was close to normal.

The weather service’s long-range models next hint at a chance of rain on Feb. 18.

The climate stations near Mineta San Jose International Airport and in downtown San Francisco are the longest operating in the Bay Area, recording highs and lows since 1893.

“Especially this month (temperatures) have been abnormally warm.”

— Meteorologist Brian Mejia