LOS ANGELES (AP) — The Latest on a statewide heatwave in California (all times local):

4:20 p.m.

The National Weather Service says San Francisco's temperature has reached 106 degrees Fahrenheit (41 degrees Celsius), breaking an all-time record high.

The weather service said Friday on Twitter the mercury hit "an incredible 106 degrees!" shortly before 4 p.m.

The previous all-time record high in downtown San Francisco was 103 degrees Fahrenheit (39 degrees Celsius) set on June 14, 2000.

The city's previous record for this day of 90 degrees Fahrenheit (32 degrees Celsius) was set in 1950.

An excessive heat advisory was in effect through Monday night for interior valley and higher elevations in the San Francisco Bay Area.

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10:15 a.m.

Dozens of cooling centers are opening throughout California and schools plan to let students out early as temperatures soar from a heat wave expected to last through the Labor Day weekend.

Forecasters say some cities in the San Francisco Bay Area are expected to see triple-digit temperatures. Livermore is expected to reach 115 degrees, a temperature last seen in 1950.

The extreme heat and light wind combined with vehicle exhaust are prompting officials to ask Bay Area motorists to limit their driving to reduce pollution. Officials say smoke from at least a dozen wildfires burning in Northern California is drifting into Bay Area skies and contributing to the unhealthy air.

The National Weather Service says an excessive heat advisory remains in effect through Monday night for interior valley and higher elevations in the Bay Area.

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6:48 a.m.

Managers of California's power grid are asking for voluntary conservation of electricity as forecasters predict more extreme heat statewide.

The California Independent System Operator predicts demand on the system will set a new all-time record Friday.

Consumers are asked to particularly cut back on use of electricity between 1 p.m. and 10 p.m., when use of air conditioners is at its peak.

The National Weather Service warns that the heat will bring a high risk of heat-related illness, especially for the elderly, the infirm and children.

Forecasters also say the heat will be dangerous to anyone without proper hydration or adequate cooling.