Sixteen patients were treated for heat related illnesses at an outdoor graduation ceremony in Brentwood Saturday morning.
Several cities in the East Bay and the North Bay zoomed past the 100 degree mark Saturday. The hottest of the hot spots was Walnut Creek which hit 112 degrees, according to the National Weather Service.
Higher temperatures were concentrated in the Pleasanton and Livermore Valley and the Napa region.
San Jose hit 100, with one report of 102 degrees in the Almaden Valley.
The coastal cities remained cooler, which is typical for the Bay Area.
The mini heatwave was short lived. Temperatures started cooling down Saturday evening as huge bank of fog blanketed the Golden Gate Bridge and headed inland.
Sunday will be significantly cooler in all areas. Thunderstorm warnings have also been issued for Sunday from 11 a.m. through 8 p.m. in inland areas of Sonoma, Napa, Contra Costa, Alameda and Santa Clara counties.
Saturday was a scorcher though. The city of Livermore hit 97 degrees by 11:30 a.m. Saturday.
A morning graduation in Brentwood ended with a string of 911 calls for ambulances after more than a dozen people fell ill because of the heat.
The Contra Costa County Fire Protection District received a call just before 10 a.m. on a report that someone had fainted at the Heritage High School graduation.
When crews arrived, they found many more patients. All are expected to recover.
The heat made water parks extremely busy. Concord's Water World was packed with families trying to beat the 105 degree heat there.
Residents were encouraged to visit air-conditioned public settings such as libraries, shopping centers, senior centers and movie theaters if they do not have air conditioning at home.
Again, the good news is that the temperatures are supposed to drop by Sunday.
Highs are expected to tumble at least 10 degrees as high pressure weakens and a cut off low pressure moves in. This cut off low will increase clouds and patchy fog as well. There only remains a very slight chance of isolated showers/tstorms with this system. It will need to be watched closely since the nature of a "cut off" low pressure is very tricky with no real path. Daytime highs will warm Inland to the upper 70s to low 80s, Bayside lower to middle 70s and at the Coast lower to mid 60s.
Temperatures greater than 110 degrees are also being forecast for this weekend in parts of Southern California including the Inland Empire, Central Valley and southern deserts, prompting state Department of Industrial Relations officials to issue a warning for workers operating outdoors.
Bay City News contributed to this report