Update Tuesday, Aug. 22: The National Weather is warning that dangerous heat will continue through at least the end of the day Thursday, and may continue into Friday ahead of a cold front this weekend. 

The National Weather Service in St. Louis has issued an excessive heat warning for the region through 10 p.m. Wednesday, with temperatures expected to climb starting Sunday.

Heat indices up to or exceeding 105 degrees Fahrenheit are likely beginning Sunday, Aug. 20 and continuing into next week. The National Weather Service predicts an over 60% chance that heat index values will exceed 105 degrees each day through the middle of next week. Prolonged hot temperatures, coupled with high humidity, poses health risks to vulnerable groups and those susceptible to related illness.

The St. Louis County Office of Emergency Management encourages people to drink plenty of fluids and to stay in an air-conditioned room out of the sun if possible. Young children and pets should never be left unattended in vehicles under any circumstances.

Anyone who works outside should take extra precautions, and reschedule strenuous activities to the early morning or evening if possible. Wear lightweight and loose-fitting clothing. The Occupational Safety and Health Administration recommends frequent breaks in shaded or air conditioned environment.

Heat stroke is an emergency and 911 should be called in the event of suspected heat stroke.