A 50 percent chance of thunderstorms is in the forecast Monday for the metro-east with the most likely chance of rain coming after 1 p.m.
Meanwhile, the high temperature is expected to reach 86 degrees and the wet, muggy atmosphere will make it seem even warmer.
But area residents will get a break from summer weather starting Monday night when a cold front moves in and pushes the low temperature to 55.
The unseasonably cooler weather will stick around throughout the week, potentially breaking records for the coolest high temperature in the St. Louis area at this time of year.
The high will be 75 Tuesday under sunny skies. The previous record for the lowest high temperature on July 15 is 77 degrees set in 1891. The low Tuesday will be 54.
On Wednesday skies will be sunny with a high of 76, slightly warmer than the record for lowest high temperature, 73, set July 16, 1958. The low Wednesday will be 56.
Skies will be mostly sunny with a high temperature of 77 Thursday. That high temperature could break the record low peak temperature of 76 set July 17, 1938. The low will be 61.