Special Weather Statement issued August 19 at 4:58AM CDT by NWS
Effective: 4:58 a.m. on Saturday, Aug. 19, 2017
Expires: 4 p.m. on Saturday, Aug. 19, 2017

...Heat Index values in the upper 90s to around 100 degrees
expected each afternoon from Sunday through Tuesday...
A weak high pressure ridge will build in across the area later
today and persist across most of the Quad State region through
early Tuesday. Only small chances for rain are expected during
this time period.
The combination of warm temperatures in upper 80s to lower 90s,
combined with increasing humidity and light winds, will set the
stage for afternoon heat index values topping out in the upper 90s
to around 100 degrees each afternoon from Sunday through Tuesday.
The highest heat index values, between 100 and 103 degrees, are
expected over southeast Missouri and extreme southwest Illinois
and Kentucky on Sunday and Monday.
The time period of greatest concern for higher heat index values
will be from 1 pm through 5 pm CDT each day.
With large numbers of people expected to be outdoors from Sunday
through Tuesday, the potential for heat related illness may
increase, especially for those not accustomed to the typical heat
and humidity of late August.
Be sure to drink plenty of water and find opportunities to keep
cool in the shade, when possible.
The heat should move out of the area later on Tuesday, as showers
and thunderstorms usher in cooler air for the middle of next week.

See more at NOAA