Temperatures in the 90s headed to Bay Area this week

The Bay Area is headed for a midweek warmup, with inland temperatures forecast to climb into the 90s Wednesday and Thursday before a cooler pattern takes hold heading into the weekend.

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Temperatures are expected to rebound Tuesday as high pressure strengthens over the region, with the warmest conditions expected Wednesday and Thursday, according to the National Weather Service’s Monday forecast discussion for the Bay Area. Inland valleys are forecast to reach the mid-80s to mid-90s, while areas around the bay should range from the low 70s to low 80s.

“We’re not expecting record-breaking heat, but it will still feel noticeably warmer inland,” Rachel Kennedy, a meteorologist with the weather service’s Bay Area office, told SFGATE on Monday.

The warmup comes as a ridge of high pressure to the south gains influence over the Bay Area. Kennedy said lower elevations should generally reach the upper 80s Wednesday and Thursday, with some of the region’s hotter spots hitting the low 90s. Higher elevations are expected to remain in the 90s.

The heat risk is expected to remain minor for most of the region, Kennedy said. Some higher elevations could see pockets of moderate heat risk because temperatures there will be warmer and overnight cooling less pronounced.

Residents closer to the bay and in urban areas should continue to benefit from the marine layer overnight. The warming will be less noticeable along the immediate coast, where marine influence will keep temperatures considerably cooler. Monday highs were forecast in the upper 50s to mid-60s along the Pacific coastline, compared with the 80s and lower 90s in inland valleys and isolated triple-digit readings in the hottest interior locations.

No rain is expected this week, Kennedy said, though morning low clouds should become patchier by Wednesday into Thursday as high pressure strengthens.

A change arrives late Thursday into Friday, when a deeper trough is forecast to build along the West Coast and push the ridge east. Temperatures should fall into the upper 70s and low 80s around lower elevations and the bay shoreline, while higher elevations should cool into the upper 80s, Kennedy said.

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The cooler pattern is expected to continue through the weekend and into early next week, accompanied by more widespread cloud cover and breezier winds. The East Bay and North Bay hills and wind-prone locations such as the Altamont Pass could see some of the stronger winds.

Forecasters are also watching Tropical Storm Iselle and other tropical systems in the eastern Pacific. Iselle was strengthening well southwest of Mexico on Monday morning and moving northwest, according to the National Hurricane Center.

“Iselle is expected to stay well out to sea,” Kennedy said. “It’ll curve northwest into the Pacific, stay away from us.” 

The storm itself is expected to remain far from the California coast, but Kennedy said long-period southerly swells generated by Iselle and other tropical disturbances could begin reaching Bay Area waters Friday and persist through the weekend.

Those swells were forecast just below beach-hazard criteria as of Monday, Kennedy said, but could increase the risk of sneaker waves and rip currents. The weather service is also monitoring whether tropical moisture could get pulled northward by the approaching trough, though forecast models differed Monday on whether it would reach the Bay Area.

With dry conditions persisting, Kennedy urged residents to remain cautious about wildfire risks during outdoor activities involving flames and to follow local restrictions on campfires and burning.

“It is fire season,” Kennedy said. “Just remember that things are dry outside.”