Oklahoma school districts have shifted gears due to the extreme heat.It was nearly two weeks into the school year for some districts when they already had to shift gears because of the heat. Many districts across the metro had recess indoors because it was so hot outside.| MORE | Oklahomans try to stay cool record high temperatures, medical heat alert When directly in the sun, add a few degrees to the National Weather Service heat index, which is what's causing local schools to switch gears in the heat."We certainly don’t recommend playing or being out for extended periods in this heat," said Rick Smith, a warning coordination meteorologist.The triple-digit heat indexes multiple days in a row did not let up this week, forcing several school districts to shift recess."Depending on the air temperature, plus the heat index, will determine whether or not we recommend if they can go outdoors or if they go outdoors with caution, or we need to go indoors," said Brad Herzer, the Oklahoma City Public Schools assistant superintendent of human resources.Over the weekend, EMSA responded to 17 heat-related calls and took 10 of them to the hospital. OKCPS, Norman Public Schools, Deer Creek and Yukon all shifted to indoor recess.Moore Public Schools modified recess, meaning students could play outdoors for up to 15 minutes. Okarche Public Schools even shifted their baseball and softball games on Monday night because of the extreme heat.Get the latest news stories of interest by clicking here."There are only short windows of time this time of the year that it's okay to be outside. Maybe before 10 o'clock in the morning or into the evenings sometimes, but during the school day, there's not a lot of safe times to be out there," Smith said.Ways to stay safe in the extreme heat are to stay hydrated, limit time outdoors and wear loose-fitting clothing.Top HeadlinesPolice, OHP bomb squad respond after grenade found in backyard of Yukon homeRoad remains closed days after train derailment in MooreOklahomans try to stay cool record high temperatures, medical heat alertVIDEO: Scenes from Southern California, Mexico as Tropical Storm Hilary hitsFamous 2-headed snake returns to zoo after injury