“Overall, we’re moving into our warmest time of year, late August into early September,” the weather service said.

The sweltering temperatures prompted a statewide Flex Alert on Friday due to an expected increase in electric demand, mostly due to residential air conditioning.

Residents are urged to conserve electricity, especially during the late afternoon and early evening, when the grid is most stressed.

Consumers are urged to set air conditioner thermostats to 78 degrees or higher, turn off unnecessary lights, and use major appliances before 3 p.m. and after 10 p.m.

The Peninsula will be under a heat advisory from 11 a.m. on Friday, Aug. 14, through 7 p.m. on Wednesday, Aug. 19, according to the weather service.

Santa Clara County is under an excessive heat watch from Aug. 14-19. The county has opened cooling centers and advised the public to drink plenty of water, stay in air-conditioned areas, whenever possible, and avoid physical activity during the hottest time of the day, 10 a.m.-3 p.m., among other actions. More hot weather safety tips can be found at sccgov.org.

The city of Palo Alto will open a cooling center at the Mitchell Park Community Center’s El Palo Alto Room from 1-6 p.m. The center is located at 3700 Middlefield Road. For more information, visit cityofpaloalto.org.

Region under Spare the Air alert on Aug. 14

The Bay Area Air Quality Management District has issued a Spare the Air alert for Friday because of excessive smog expected in the region.

The alert, the third issued by the air district for smog this year, is the result of a forecast of light winds and temperatures of up to triple digits in inland parts of the Bay Area that will combine with vehicle exhaust to create an unhealthy level of smog, otherwise known as ozone.

Smog can cause breathing problems and other medical maladies, so the air district encourages Bay Area residents to only exercise outdoors in the early morning hours when smog concentrations are lower, as well as to work remotely and avoid long car trips to limit the levels of vehicle exhaust.

People can find out when a Spare the Air alert is in effect by visiting sparetheair.org, calling 800-HELP-AIR (4357-247), downloading the Spare the Air smartphone app for iPhone or Android devices or connecting with Spare the Air on Facebook, Twitter or YouTube.