Getting Hot in Here

... so take off all your clothes.

Characters are Locked in a Room, and the temperature's rising to Sauna of Death levels. They decide to take a few clothes off to get comfortable (but not necessarily "get comfortable").

Often, but not quite always, done for the purpose of Fan Service.

A frequent variation is to have the characters being discovered in a state of entirely innocent dishabille by rescuers who immediately assume they've been taking advantage of time while waiting for the rescue.

Another variation involves deserts, which would actually be a bad idea in real life, on account of loss of bodily fluids, sunstroke, etc. -- the stereotypical Arabic costume of robes and head-dress exists for a reason.

Examples of Getting Hot in Here include:

Hot Room variant

Advertising

A Kraft Dinner commercial had this. The landlord says to two college roomies that "there will be no microwaves or hotplates in the room", prompting them to turn up the thermostat to cook the mac n' cheese. When one asks the other "think we should turn the heat down now?", the other sees the hot women walking through the halls in their undergarments fanning themselves sexily. You can guess the response.

Anime and Manga

Averted in Neon Genesis Evangelion, when Misato refuses to take off anything with Kaji also present in the elevator, despite it really getting hot. Then again, it's mentioned several times that they used to date and went through a painful break-up, so it makes sense from her point of view.
This happened in the hot room challenge from Kujibiki Unbalance (the one where they told scary stories).
In The Big O episode "Call From The Past", Angel and Roger Smith are trapped in a building underwater. Angel takes off her dress (leaving her in her lingerie) and afterwards is shown fanning herself, indicating that she did it because she was feeling hot. It starts around 3:55 on this YouTube video. BTW, this is Fan Service, an indication of UST, and a way for Roger to see the scars she has on her back. :)
Happens near the beginning of the anime Please Teacher! when Kei and Mizuho are locked in the gym storage room.
Done on purpose by Naru's little sister Mei in Love Hina, in order to get Keitaro to notice Mutsumi more.
Happens rather late into Hayate the Combat Butler. While Maria tries to show Hayate the old mansion sauna, the lights go dim and they both trip and get stuck to the floor. The temperature was unbelievably high and they tries to get out but Maria got her skirt stuck to the floor forcing her to take it off (and forcing Hayate to look away). Sadly, Haytate accidentally sees her panties and is thrown in the dungeon for the remainder of the day.
The Radio Drama of UFO Princess Valkyrie has a two-episode story where child Valkyrie accidentally traps everyone inside an improvised sauna. All of the girls (except for Akina, of course, due to the presence of Kazuto as well as Risa for being absent the entire radio series) remove their clothes to cool off. Somewhat subverted in the fact that Akina actually does start getting dangerously dizzy and faint from the heat due to not stripping.
In A Certain Scientific Railgun Kiyama Harumi tends to use this trope whenever it gets hot, far below Sauna of Death levels. She is always stopped by other female characters about halfway through.

Film

The Fantastic Four film had Johnny repeatedly utilizing his newfound powers to put this trope in action while riding in a elevator.
Christmas at the Riveria, a 2007 Christmas drama, features the Mistaken for Cheating variaton.
In Ace Ventura: When Nature Calls, things got a bit hot for the title character whilst spying on someone from within a tank disguised as a rhino. After stripping bare, he finds that the tank door is jammed, so he crawls out through the rhinobot's vagina, meaning that a safari-going family got to witness a rhino giving birth to a fully-grown, naked human.
Betsy Parker's character does this to herself - deliberately turning up the heat to give her an excuse to disrobe - in the 1983 teen sex comedy Private School.

Literature

Nancy Drew, of all people, gets caught in this trope during Two Points to Murder when she's locked in a basketball team's sauna. She removes shirt, jeans, socks and shoes, which (though it's not expressly mentioned) leaves her in her underwear when she finally figures out how to escape.
Arthur C. Clarke's A Fall of Moondust: A tourist moonbus, buried under several metres of dust has its air conditioning fail, because the radiators are buried, leading to all of the passengers shedding most of their clothing.

Live-Action TV

This might be the reason Nyssa takes off her skirt in the Doctor Who serial Terminus but it was so out of the blue and poorly explained that it has become a running joke among Doctor Who fans.
Primeval
- Season 1 has Abby keeping her pet lizard Rex in tropical temperatures, requiring her to walk around in her underwear. A new season and a change of timeline later, she seems to have lost the habit.
- Helen justifies her usual lack of clothing as her travelling in historical eras where it is much hotter than the present.
Friends parodied this, with Joey turning up the thermostat:

Rachel: It must be like 100 degrees in here!
Joey: Is it so hot you want to walk around in your underwear?
Rachel: No!
Joey: Still not enough!

(The middle lines are often cut in re-runs, resulting in a rather odd non-sequitur.)

Done completely straight in a Season One episode of Ashes to Ashes, with Alex Drake and Gene Hunt locked in a secure and near-airtight document vault. Alex strips down to her underwear and Gene breaks out a hip-flask just in time for Ray and Chris to arrive and break them out.
Played for laughs in Monty Python's Flying Circus with a scene outside a tower block with a young lady changing in the window (and the lines "My it's hot in here" badly dubbed on). Later this scene is itself parodied where Ramsay MacDonald is the "My, it's hot in here" stripper.
Spoofed in the recurring Saturday Night Live segment "How Do You Say?....Ah, Yes!....Show," where Chris Kattan played a very randy Antonio Banderas. The sketch always ended with Kattan "innocently" remarking "It is hot in here, no?" and tearing off his shirt to the accompaniment of a flamenco guitar before trying to "seduce" (i.e. date-rape) his female guest.
In an early episode of Farscape, an alien decides to lay eggs and hatch its young in Moya, and has to increase the heat in order to properly incubate the eggs properly. Aeryn ends up going into heat delirium (a potentially fatal condition her species is susceptible to, due to their being unable to deal with excessive heat). She does her best to lower her body temperature by removing some clothing, followed by taking a cold shower. Since heat delirium is apparently a very unpleasant way to go, this is not played for Fan Service.

Music

The song "Hot in Here" by Nelly. And the video clip, of course.

Western Animation

Code Lyoko: Used to play up the UST for all it was worth between Ulrich and Yumi in episode "New Order".
- And to much frustration, they still remained Just Friends
Seen in Futurama when Fry and Bender flood their prison cell with steam and decide to use it as an actual sauna.
- Also when Amy and Fry get stranded on Mercury in her new car.
Happens in the French animation show Once Upon a Time... Space, at the beginning of the Revenge of the Humanoids story arc. The spaceship of Pierrot and Psi crash-lands on a desert planet and the internal heat regulator is busted, leading the male and female leads to strip off their tops. The desert part of the trope is then averted when they venture outside, though, as they wear heat-repellent suits.
In The Marvelous Misadventures of Flapjack, Flapjack and K'nuckles climb a mountain and assume it's going to be hot at the top because it's closer to the sun, so they do this. Of course, they were wrong about the top of the mountain being hot....

Desert variant

Comic Books

Happens in Little Ego, where Ego's guide recommends she remove her clothing. Justified Trope as it occurs in an Erotic Dream. As she is disrobing, the scenery changes around her and she finds herself performing a striptease on stage.

Live-Action TV

Primeval: Possible reason why Helen's clothes are all torn, but not sufficient reason why she hasn't popped into one of the many clothes shops she's bound to have encountered in the 21st century.

Web Original

In Broken Saints, Oran takes his shirt off when crossing the desert... at night, when it would be very cold. (Considering he lives in that climate, you think he'd know better.)