High temperatures could be in place in several of the host cities during the World Cup.
Peak heat indices are forecast to be in the 100-110 degree range, the NWS said.
Extreme heat blanketed the Chicago area with heat index readings up to 110 on Thursday. Severe storms almost moved through parts of the area, leaving damage, and more are expected this weekend.
Extreme heat is blanketing the Chicago area starting Wednesday, with heat index readings expected to be up to 110.
The Chicago area will go experience dangerous temperatures and humidity both Wednesday and Thursday.
There was a special honor Thursday for a World War II veteran who died alone during Chicago's 1995 heat wave.