Oppressive heat and humidity are on the way.

The National Weather Service in Cleveland has issued an excessive heat watch for Friday afternoon through Saturday evening for 22 counties across northern Ohio, including the Akron area.

Heat indices — which combine temperature and humidity — may range from 105 degrees to as high as 112 degrees on Friday and Saturday afternoons, creating dangerous conditions that could lead to heat illnesses. The worst conditions will be in the Toledo and Findlay area, said Patrick Saunders, a meteorologist with the National Weather Service.

Akron will keep several community centers open with extended hours Thursday, Friday and Saturday to serve as "cooling centers" where people can escape the heat. The following community centers will be open from 8:30 a.m. to 9 p.m.:

• Lawton Street Community Center, 1225 Lawton St.

• Mason Park Community Center, 700 E. Exchange St.

• Patterson Park Community Center, 800 Patterson Ave.

• Summit Lake Community Center, 380 W. Crosier St.

“We also encourage all our residents to check in on their neighbors and family members who may be vulnerable to these high temperatures, and take steps to keep children and pets well hydrated, rested, and out of the sun," Akron Mayor Dan Horrigan said in a prepared statement.

The National Weather Service warned that vehicle interiors could reach lethal temperatures within minutes and to never leave pets, children or the elderly unattended in parked vehicles.

Summit County Health Commissioner Donna Skoda recommends avoiding outdoor activities.

"Your chores can wait," she said. "You can garden, pull your weeds, cut your grass another day. This isn't the time to be outside doing a lot of strenuous work in the heat of the day.

She offered other ways to survive the heatwave. See the accompanying box.

Akron-based FirstEnergy Corp. reported that it is prepared for the high heat. The utility also posted a lengthy list of tips for customers at its website at firstenergycorp.com/newsroom/featured_stories/summer-heat.html.

The tips include setting thermostats as high as comfort allows; using a programmable thermostat; closing drapes and blinds; using fans; and avoiding using heat-producing appliances.

"Be conscious about how you are using electricity so you don’t get the shock when the bill comes after the high heat," company spokeswoman Jennifer Young said.

The electric department for Cuyahoga Falls is urging all city customers to reduce their electric usage from 2 to 6 p.m. Thursday and Friday, with temperatures expected to reach more than 90 degrees both days.

A portion of Cuyahoga Falls' rates are the result of transmission and capacity charges, which are based off community-wide electric demand on the hottest days of the year — demand peaks. By lowering electric usage on those days, customers can help keep electric rates lower in the future, according to a city news release.

Customers can reduce their electric usage by shutting off lights when leaving unattended rooms; raising the thermostat by several degrees; closing curtains and blinds; saving laundry, dishes and other household chores until later in the evening; turning off and unplugging unused electronics and appliances; and grilling out instead of cooking indoors, the release said.

Conditions are expected to improve Sunday, with a high of around 90 degrees and less humidity.

"It’s not going to be perfect but it’s going to be a little bit better," said Saunders from the National Weather Service.

The temperatures are expected to fall into the mid to low 80s on Monday.

The National Weather Service noted that it hasn't issued an excessive heat warning — which comes when temperatures soar over two days and the overnight temperature doesn't fall below 75 degrees — since 2012.

Officials at the FirstEnergy All-American Soap Box Derby are discussing how to help the racers, their families and fans cope with the expected high heat. Hundreds of racers and their families from around the United States and elsewhere in the world are in Akron this week for the championship races at Derby Downs.

The race is not prepared to bring water misters out that can help provide relief from hot weather, said Mark Gerberich, derby president and chief executive.

“We don’t have access to water where we really need it,” he said. “We don’t have the big misters to put out. We’re still working on possible other solutions as we look into Saturday.”

Racers will get water in their packets and the derby will have water stations for them and their families to use, he said. In addition, wet towels will be provided to the competitors to put around their necks, he said.

Derby Downs does not have shelter for fans when the weather is severely hot, Gerberich said.

“I’m more concerned now for the fans now that we’ll get 96, 97 [degrees] and they’ll be out here and there’s no cover for them,” he said. “I think the concessionaires are going to be really happy with us this weekend.”