A surge of cooler air moving up from the Central Coast will bring lower temperatures to much of the Bay Area starting Friday, especially near the coast and bay.
But the heat will not disappear everywhere at once.
Marine air will have a much bigger influence in San Francisco, along the Peninsula and the bayfront, where Friday should feel significantly cooler than Thursday. Farther inland, especially in the interior East Bay, North Bay and Santa Clara Valley, the cooldown will lag. Many valleys will stay warm to hot Friday before more relief arrives Saturday and Sunday…