In the latest version of Prison Architect (Update 4), a fire incident had recently occurred. But after the fire was put out, now there is extreme heat and cold throughout the entire prison. I can't figure out how to "cool down" the hot sections (there are no flames), and creating radiators for the extreme cold doesn't seem to work either. I've attached some screenshots.

This is why I'm afraid to go back to it since the last upgrade! :P

I had a similar problem, a fire spread from the kitchen to the canteen, where the temp hit 390 F and stayed there. It's been cooling off around 10 degrees or so a day, as three days later it's now 360 F.

If that's too slow, bulldoze a section of the room, opening it to the outside. I opened up a 2x2 section in the center of the canteen, and the temperature rapidly approached normal, spreading through all the overly hot areas. I don't know if that'll work with the extreme cold, but it's worth a shot.