Large portions of the Bay Area and the Central Coast were under a heat advisory Thursday morning, which has been extended for what could be the hottest days of the year.

Parts of the Bay Area were baking under triple-digit heat on Thursday, with at least seven cities notching new daily records, the National Weather Service said.

The onset of what will be the longest, most intense heat wave of the summer thus far arrived a bit warmer than the National Weather Service anticipated, and weather forecasters said temperatures may rise above expected levels again on Thursday.