3 low-pressure weather systems to impact California. Here's what that means.

Photo of Amy Graff
California is expected to see cool weather into next week. This file photo shows the San Francisco Golden Gate Bridge hugged by fog.

California is expected to see cool weather into next week. This file photo shows the San Francisco Golden Gate Bridge hugged by fog.

Angela Nasimi / EyeEm/Getty Images/EyeEm

Unseasonably cool weather is in the forecast across California through the Fourth of July holiday weekend and into next week with three low-pressure systems expected to impact the region, the National Weather Service said.

Below-normal temperatures, ocean breezes, coastal fog and light drizzle are all in the mix. There's even a chance of rain in the most northern parts of the state. 

"The first low-pressure system is today," said Drew Peterson, a forecaster with the weather service's Monterey office. "It's mainly over the Pacific Northwest. Northern California is just getting clipped by this one. There's a bigger system coming in through the weekend, it's the strongest of the three. That's the one that could bring drizzle. That's why it's going to be cooler. There's a third one coming in next week. That one is also mainly over the Pacific Northwest."

The mild weather is forecast to continue into next week with a warm-up expected the weekend of July 8.

This back-and-forth between warm weather and unseasonably cool temperatures has been an ongoing trend in California in May and June. The breaks from the heat have helped slow down the state's progression into peak wildfire season, though the season has picked up with the Edgewood Fire triggering evacuations in San Mateo County last week and the Rices Fire exploding in Nevada County on Tuesday afternoon.

Below-normal temperatures are in the forecast for San Francisco over the Fourth of July holiday weekend. This file photo shows flags on the front porches of the homes at Fort Baker on July Fourth.

Below-normal temperatures are in the forecast for San Francisco over the Fourth of July holiday weekend. This file photo shows flags on the front porches of the homes at Fort Baker on July Fourth.

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Fog could impact Fourth of July fireworks in the Bay Area

Cooler temperatures and fog will dominate the forecast across the San Francisco Bay Area into next week.

"On Saturday and Sunday mornings, we could see a drizzle fest on the coast," Peterson said. "I wouldn't be surprised if we got drizzle at some places along the bayfront too, like in Oakland."

Sunday is forecast to be the coldest day of the week in the region, with upper 50s to low 60s along the bay shore, mid- to upper 60s along the bay front and mid-70s in interior valleys. 

Afternoon highs on Monday, the Fourth of July holiday, are forecast to be 3 to 5 degrees warmer than they were on Sunday. 

Fog is likely to blanket the Bay Area on Monday evening, especially along the coast. 

"It looks pretty cloudy," Peterson said. "Because we will have low pressure over the area, it is possible the cloud ceilings won't be near the surface, that might be enough for fireworks. As long as we're at ceilings of 900 feet, we might be able to have fireworks. If there are any fireworks being set off by cities, hopefully they can be set off at lower altitudes so they can be seen."

Rain is in the forecast for far North California

 While the San Francisco Bay Area is unlikely to see any actual rain, parts of far Northern California could.

As the low-pressure system moves onshore Saturday, a chance of light showers enters the forecast over Shasta County. Along the Northern California coast, showers are possible on both Saturday and Sunday. 

"Some showers will be possible by Saturday afternoon, but the better chance will be on Sunday, particularly for interior areas
north of Cape Mendocino," the Eureka weather service office said in its forecast. "Thunder probabilities increase for northeast Trinity as the trough deepens on Friday, but the best chance for an isolated thunderstorm will be Saturday during the late afternoon hours (but still less than 20%)."

In the Sierra Nevada, the Tahoe Basin is expected to see mostly sunny skies at the start of the weekend, with temperatures gradually cooling, Eric Kurth, a forecaster with the weather service's Sacramento office, said. Afternoon highs around the lake are expected to range from 71 to 81 on Friday and gradually cool through the weekend, with a high of 66 to 67 on Saturday and 62 to 72 on Sunday.  

"It will be quite a change," said Kurth. "We've been above normal in Tahoe for a while." 

Even Southern California will see below-normal temperatures

The weather story in Southern California also includes below-normal temperatures. Cooling is expected to start Thursday and continue through the weekend with fog hugging the coast.

Sunday is also forecast to be the coolest day of the week in SoCal, with with coastal temperatures in the upper 60s to mid-70s and valley temperatures in the upper 70s to mid-80s.

"These temperatures are 6 to 12 degrees below normal," the weather service's Los Angeles office said.

Temperatures will begin to climb in Southern California on Monday and even more so on Tuesday as high pressure over Texas expands westward, the weather service said.