From Weather Underground:
… Excessive heat warning in effect from 7 am Thursday to 7 PM CDT
The National Weather Service in St Louis MO has issued an excessive
Afternoon high temperatures will rise near 100 degrees with heat
indices ranging from 105 to 115 degrees. Overnight low temperatures
are only expected to drop into the upper 70s… which will provide
little relief from the daytime heat.
An excessive heat warning is issued when high temperature and
humidity levels are expected to make it feel like it is 105 degrees
or greater for 3 or more consecutive days.