Even in places where power was not disrupted, people with no air-conditioning were advised to spend the day in a library, a cooling center or some other such place to avoid heat exhaustion.
The U.S. Centers of Disease Control and Prevention was among many government agencies trying to keep people informed -- from knowing when the food in your suddenly inoperable freezer can't be eaten to taking a cool bath if you don't have AC.
The Jackson County medical examiner in western Missouri, for instance, was investigating three deaths that may be related to the heat, according to the Kansas City Health Department.
"Current indications are that this heat wave will continue well into next week, though there is still some uncertainty in the forecast," the National Weather Service said in its warning around St. Louis. "The effects of excessive heat are cumulative... Take action to protect your health."