We spent some time with people for whom 99-degree heat is only just the beginning of what they endure during their workday.
With 75 pounds of gear on his back and 99 degrees of sticky heat surrounding him, Billy Meyer did what firefighters do: face down a 1,000-plus degree inferno.
"Just like a blowtorch," said Chicago firefighter Billy Meyer. "It's just like walking into a blowtorch."
The blaze threatened to consume half a block. More than 100 firefighters responded. Due to the heat, they rotated in and out every ten minutes.
"That's 1,200 degrees when you're looking at the fire," said Chicago Fire Department Deputy Commissioner John McNicholas. "So, when we're wearing 75 pounds of gear, and our body temperatures are starting to push that 100-plus level, we're cooking on the inside."
"If you're not careful it can shut down, so you've got to be aware of that. Now, thank god you've got guys behind you that'll help you," said Meyer.
Whether it's fighting fires in the city or practicing on the football field in the suburbs, the message is the same: hydrate.
"We tell kids - you need to step out of something, step out, but remember you gotta get back in because you'll be playing on nights that are just this warm," said Greg Purnell, football coach at St. Francis High School in Wheaton.
"You're already about 3 percent or 5 percent dehydrated when you start to feel that sensation of thirst so you're already kind of behind the ball," said Dr. Jeff Mjaanes of Rush University Medical Center.
Words many lived by today - especially those who can't - and wouldn't want - to be doing anything else.
"There's too much pride, especially over here on the West Side," said Meyer. "These guys are full of pride, they never give up. Never."
Many of those firefighters we met on the Southwest Side Tuesday were just starting their 24 hour long shifts.
I checked back with the guys at engine 38, and around 9 or 10 p.m. they were back out fighting another fire.