(CBS SF) – The National Weather Service said the Bay Area will experience a prolonged heat wave from this weekend through the middle of next week, and has issued an Excessive Heat Warning for inland areas in the East Bay and South Bay.

The heat warnings and watches issued by the NWS have led the California Independent System Operator (ISO) to call for voluntary electricity conservation by the state’s residents, putting out a statewide Flex Alert from 3 p.m. to 10 p.m. on Friday.

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The state ISO noted that the forecast high temperatures have the power grid operator predicting a spike in electricity demand, primarily from residential air conditioning use.

Consumers are urged to conserve electricity, especially during the late afternoon and early evening when the grid is most stressed due to higher demand and solar energy production falling. Consumers should also consider turning off unnecessary lights, using major appliances before 3 p.m. and after 10 p.m., and setting air conditioner thermostats to 78 degrees or higher.

More information on Flex Alerts and electricity conservation tips are available at the ISO’s Flex Alert website.

In addition, the Bay Area Air Quality Management District issued a Spare the Air alert for Friday, saying light winds combined with triple-digit inland temperatures and vehicle exhaust are expected to cause unhealthy smog accumulation in the Bay Area.

The heat warning, which goes into effect at 11 a.m. Friday and extends through 9 p.m. Wednesday, covers the interior East Bay Counties, the South Bay the East Bay interior valleys, East Bay Hills and the Diablo Range, along with the Santa Clara Valley including San Jose. The warning also covers inland areas of Monterey and San Benito counties to the south of the Bay Area.

“Due to the long duration of this event, accumulating heat stress will be a significant impact for the general public, pets, vegetation, and livestock across the region, particularly those sensitive to the heat,” the weather service said.

Afternoon highs inland could range from the mid-90s up to 105 degrees starting Friday and through this weekend, possibly extending into next week, the weather service said.

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On Thursday, temperatures in East Bay cities like Walnut Creek and Concord were already topping 100 degrees. When you add a heat wave to a pandemic, even the simple act of cooling down becomes complicated.

During a typical heatwave, a cooling center KPIX 5 visited in Pleasant Hill would be able to provide cold water, snacks and air conditioning for 52 people. With COVID-19 social distancing protocols, that number is slashed to only 11.

“The senior cooling center, the malls, a lot of the shops where people would go to get away — Starbucks, McDonald’s — those are closed for access. So people can come here and sit,” said Sandy Bustillo from the Contra Costa County Employment and Human Services Department.

Outdoor dining — the lifeline for many restaurants in the pandemic — suddenly has an additional burden.

Sunrise Bistro and Patio in Walnut Creek spent $12,000 getting their patio and parking lot ready for outdoor dining, only to add another cost Thursday. The owners installed misters to keep their customers cool.

“We have 12 pop up canopies to hopefully help with the heat. We add the misters and hope for the best,” said Sunrise Bistro co-owner Joe Stein.

Meanwhile, the rest of the Bay Area, including the North Bay interior valleys, areas around the San Francisco Bay, along with the Santa Cruz Mountains will be under a Heat Advisory. Afternoon highs in these areas could reach the 90s and possibly the 100s.

Overnight lows will range from the upper 50s to the 70s in the hills, which may limit relief from the heat, officials said.

The weather service urged people to drink plenty of fluids, stay out of the sun and in an air-conditioned room if possible, and to check up on relatives and neighbors. Children and pets should not be left in vehicles.

People working or spending time outside during the advisory should also take extra precautions, and strenuous activities should be rescheduled to the early morning or evening. Anyone heading to the coast for relief should also beware of potential rip currents.

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Andria Borba contributed to this story.