Heart of Ice - S1-E3
Corrected entry: Mr. Freeze's cell at Arkham Asylum has been modified to accommodate his inability to survive outside of sub-zero temperatures, but his cell has a barred window which could easily allow warmer weather to interfere with the temperature regulation (the episode's opening scene states that Gotham is in the midst of the hottest August on record). (00:21:00)
Correction: A single small window even in an area of high heat would not be able to interfere that much in a sub-freezing room with a dedicated hyper-cooling system.
Greg Dwyer