(CNN) -- A heat wave in Missouri and other parts of the Midwest kept temperatures could have the index reach triple digits on Tuesday and likely the rest of the week.
Temperatures in the St. Louis area started off in the mid-70s but were expected to reach a high of 97 by the afternoon. But News 4 Meteorologist Kent Ehrhardt said it will feel more like 100 degrees.
The record high for this date in the St. Louis area is 102 degrees.
In addition to Missouri, heat warnings and advisories are in effect for seven other states: North Dakota, South Dakota, Nebraska, Illinois, Wisconsin, Iowa, Minnesota and Missouri.
On Monday, the heat index in Iowa reached 110 degrees, Iowa’s Department of Public Health said, and it warned residents of the risk of heat-related illnesses. It said even young and healthy people could be affected if they are active in hot weather.
The high temperatures are forcing a number of school districts across the region to make changes to their schedules.
Minneapolis Public Schools canceled all after-school activities and athletic practices Monday because of the heat, the district said.
Five elementary schools in Fargo, North Dakota, are closed through Wednesday because they are not air-conditioned, said Jeff Schatz, the superintendent of Fargo Public Schools. He said he was in one of the buildings at 6 a.m. Monday and the inside temperature was already close to 85 degrees.
The closures affect about 1,300 students in kindergarten through fifth grade, he said.
A malfunctioning air conditioner compressor in a Sioux Falls, South Dakota, elementary school forced teachers to dim the lights, close the blinds and use fans to keep things cool, said Sioux Falls School District spokeswoman DeeAnn Konrad.
Plans are in place to move children in the affected classrooms to an air-conditioned private school across the street, she said.
In hard-hit Iowa, schools in the central city of Marshalltown dismissed at midday Monday and planned to do the same Tuesday, school district spokesman Jason Staker said.
“Not all of our schools have buildingwide air conditioning,” Staker told CNN. “When the temperatures outside reach into the high 90s like they did today, it doesn’t take long for the temperature to rise in a classroom, especially when it’s full of students.”
The cause of the heat wave is unusually strong high pressure over the northern Plains and parts of the Midwest, Hennen said.