The St. Louis National Weather Service office has issued a heat advisory for Monroe County and Randolph County effective until 7 p.m. Sunday night. An excessive heat warning has been issued for St. Clair County and a majority of the STL metro area.

From the NWS bulletin:

* TIMING…DANGEROUS LEVELS OF HEAT AND HUMIDITY WILL CONTINUE
FOR THE REST OF THE WEEK AND INTO THE UPCOMING WEEKEND.

* HEAT INDEX VALUES…UP TO 105 DUE TO TEMPERATURES IN THE 90S
AND DEWPOINTS IN THE LOWER 70S.

* IMPACTS…THE COMBINATION OF HOT TEMPERATURES AND HIGH
HUMIDITY WILL LIKELY LEAD TO AN INCREASED RISK OF HEAT-
RELATED STRESS AND ILLNESS. THE VERY YOUNG… THE ELDERLY…
THOSE WITHOUT AIR CONDITIONING…AND THOSE PARTICIPATING IN
STRENUOUS OUTDOOR ACTIVITIES WILL BE THE MOST SUSCEPTIBLE.
ALSO…CAR INTERIORS CAN REACH LETHAL TEMPERATURES IN A MATTER
OF MINUTES. BEAT THE HEAT… CHECK THE BACKSEAT! NEVER LEAVE
CHILDREN OR PETS UNATTENDED IN A VEHICLE…NOT EVEN FOR A
MINUTE.