When will the Delta breeze reach Sacramento? Here’s how high temperatures need to climb

EDITOR’S NOTE: The following excerpt was originally published on May 27, 2022, in Bee Curious, a community-driven series where reporters answer reader questions. It has been edited for context.

The Delta breeze — a sea breeze that comes inland from the San Francisco Bay — typically blows into Sacramento in the afternoon and early evening in the warmer seasons, according to climate and weather experts.

This includes late spring to early fall, said Hannah Chandler-Cooley, a meteorologist with the National Weather Service in Sacramento. She added that the cool gusts have coasted through Sacramento as early as April.

Air currents from the Bay and North Bay-Napa area drift through the Carquinez Strait, said Ian Faloona, an atmospheric scientist and professor at the University of California, Davis. Then, they come inland, feeding both the Sacramento and the San Joaquin valleys.

It’s a localized effect caused by the difference in land and ocean temperatures nearly 100 miles away.

How hot does it need to get to feel the Delta breeze?

“Usually when temperatures approach 100 degrees — between 90 and 100 degrees — in the late afternoon, that’s enough to kick in the Delta breeze,” said Bill Patzert, a climatologist who retired from NASA’s Jet Propulsion Laboratory in Pasadena after nearly 35 years. “The irony is that the hotter it is, the stronger the breeze.”

Once the breeze comes in, temperatures can cool down three to six degrees, Patzert said.

According to past forecasts, the Delta breeze can bring gusts up to double digits in certain areas. Chandler-Cooley said weaker breezes can be around 20 to 25 miles per hour, whereas stronger winds have gusts up to about 35 miles per hour.