(CNN) -- Searing temperatures kept their grip on only three southern states -- Louisiana, Oklahoma and Texas -- on Thursday evening, according to the National Weather Service.
At the peak of the past week's heat wave, more than 20 states from the Plains to the Northeast were under heat advisories.
Topeka and Wichita, Kansas; Kansas City, Missouri; Hastings, Lincoln and Omaha, Nebraska; and Oklahoma City and Tulsa, Oklahoma, are among cities under an excessive heat watch for Friday through Sunday.
The heat wave across the South is forecast to move north over the weekend. Extreme heat indices -- how the air feels, with heat and humidity -- are expected to reach up to 116 degrees in Minneapolis, Minnesota, next week.
"These are extreme out-of-the-ordinary temperatures for Minnesota," CNN meteorologist Sean Morris said.
Dallas, Fort Worth, Arlington and other areas in Texas experienced afternoon heat indices of 105 degrees or more through Thursday.
The month of June was the hottest recorded for Texas since 1895, according to the National Weather Service.
Lawton, Oklahoma, and Wichita Falls, Texas, shot past the 100 mark for the area's 16th consecutive day of triple-digit heat Thursday.
In Oklahoma City, forecasters are calling for nearly another full week of temperatures near or above 100 degrees, threatening to break a 1936 record for 22 consecutive days of such heat.
The heat has driven demand for water up and shrunk soil, resulting in low water pressure and burst pipes in Oklahoma City. Officials issued mandatory water-use restrictions for the first time in at least a decade, according to utilities department spokeswoman Debbie Ragan.
More than 200 people have suffered from heat-related emergencies in Tulsa and Oklahoma City since June 17, when the agency issued its first heat alert, said Lara O'Leary, spokeswoman for the Emergency Medical Services Authority of Oklahoma.
Forecasters say people should limit outdoor activity during the hottest times of day, wear lightweight clothing, drink plenty of water and watch for signs of heat exhaustion, which include heavy sweating, pale and clammy skin, a weak pulse, fainting and vomiting.
CNN's Sean Morris, Dave Hennen, Ed Payne and journalist Craig Johnson contributed to this report.