Severe heat across much of the US has claimed at least 22 lives around the country, officials say.
Families in St Louis were forced into unorthodox ways of cooling off
At least 10 states have suffered heat-related deaths as a swathe of the US has sweltered above 38C (100F), although temperatures are set to fall.
Four people died in Chicago, raising the city's toll to seven.
Other deaths have been reported in Philadelphia, Oklahoma City, Arkansas, Indiana, South Dakota and Tennessee and Wisconsin, AP news agency reports.
Storms brought down power lines in St Louis, Missouri, cutting air conditioning units and forcing the National Guard to evacuate residents.
Missouri Governor Matt Blunt ordered in the National Guard in a bid to restore electricity and move sweltering citizens to buildings with emergency air-conditioning.
"We can't overstate the danger of this heat," said Francis Slay, mayor of St Louis.
"I've never seen this many people without power, this much debris, buildings collapsed, lines down."
The St Louis heat was expected to subside on Friday, with milder temperatures forecast in the days ahead.