Heat wave hits peak

Temperatures rise into triple digits Wednesday but set to drop

As an inland Bay Area heat wave peaked Wednesday, forecasters warned that thunderstorms are expected to move into some parts of the region Thursday night.

A slight chance of thunder is expected Thursday evening in parts of the South Bay and possibly in San Francisco, said Will Pi, a meteorologist with the National Weather Service.

The storms would come after a two-day stretch of excessive heat, when temperatures in inland cities like Concord and Livermore reached triple digits on Tuesday and neared triple digits on Wednesday, Pi added.

“It just gets progressively warmer as you go inland,” Pi said.

Concord topped out at 98 degrees Wednesday and Livermore at 99.

The North Bay valleys also felt the heat Wednesday. Calistoga hit 101 degrees and Cloverdale 102.

The hottest time of day “varies from day to day, but in a pattern like this the hottest time of day is between 3 to 5 p.m.,” said Duane Dykema, a meteorologist with the National Weather Service.

Temperatures in San Francisco and parts of the East Bay closer to the bay were 74 Wednesday and expected to stay relatively the same through Friday before cooling down

“It just gets progressively warmer as you go inland.” Will Pi, National Weather Service meteorologist

for the weekend, said Dykema.

In Hayward, temperatures crept into the high 80s Wednesday and in Fremont they hit the low 90s.

The South Bay also was in the low 90s. Cities farther south were hotter; Gilroy reached the mid-90s and Morgan Hill 102.

In eastern Contra Costa County, Antioch hit 100 and Brentwood 104, but both are expected to dip back to the mid-90s for the rest of the week.

That cooldown is expected to sweep into the Bay Area starting on Thursday, though Pi warned it will be slight.

Temperatures throughout the Bay Area will be just a few degrees cooler than on Wednesday, which Pi said will be the hottest day of the week.

Forecasters warned that residents should not leave pets or children in cars during the heat wave. They suggested checking on the elderly, sick and those without air conditioning.

Limiting strenuous outdoor activities and staying hydrated are also recommended, especially for those with respiratory conditions, according to the Bay Area Air Quality Management District.

Liam Molampy, 8, of San Francisco runs through water sprays at a playground in Dublin, where temperatures hit 100 Wednesday afternoon.

Michael Macor / The Chronicle Jaelynn Thomas, 9, of Hayward ambushes Kekoa Juvera, 12, while playing in Don Castro Regional Park in Castro Valley, where temperatures climbed to 93.