Temperature

Temperature is an aspect of life on the station that many people don't think about until it kills them. Almost always you will be kept at a comfortable temperature thanks to Atmos, but things can and do go wrong. You can check the surrounding temperature with your PDA. All temperatures are recorded in Centigrade.

Heat

High temperature can occur for a few reasons. Typically it means there is a fire somewhere. You will personally overheat if you are fat and overexert yourself. You will be warned that you are burning alive by your sidebar, and the message "You feel a searing heat scorch your lungs!"

This is how heat works on the station:

Heat will pass through windows, grilles, glass doors, and airlocks.
If you are next to a room that has a plasma fire with windows between you, the heat will very quickly transfer into your room. You won't burn in the fire, but you will be oven roasted you if you are foolish enough to remain.
Heat kills extremely quickly. Once you get the searing heat message, get as far away from the fire as you can. Don't bother going back for anyone else, if they have collapsed, the heat is already so intense you will surely die before you can get there and back again.
The firesuit will provide protection to the heat of a fire. It will not work without a Fire Helmet or Hard Hat with it.
Walls and floors can heat up as well, but heat will not transfer through them. An intense enough fire will melt the floor away though, opening the room to space.
A hot fire will spread a plasma fire to an unlit, adjoining room, so long as their is enough plasma to light in the adjoining room. Fire doors will not stop this.
Heat can be caused by extremely high pressures.
Heat can be contained in canisters and used for bombs.

Fire

Fire is hot. People know this. You can be set on fire under certain circumstances, such as a crazed assistant drenching you in welding fuel and lighting you with a cheap lighter. If you are on fire, your temperature will rise and you will take constant burn damage. Fire is signified by flames all over your character's body. You can put yourself out by pressing the Resist button, causing you to drop on the floor for a few seconds as you roll yourself out. Fire extinguishers, showers and the VOID OF SPACE also put out fires.

Cold

In space, no one can hear your teeth chatter. Space is very, very cold, and going out into a vacuum will cause you to die of freezing before you die of depressurization. This is what makes spacewalks so deadly, even if you have internals. Warm yourself with a hot drink or just returning to a part of the station with air. You will be warned of cold by your sidebar, and the message "You feel ice-sickles forming in your lungs!"

This is how cold works on the station:

Coldness slows your body down. In space, this can be fatal. In cryogenics, this can save your life.
The colder you are, the slower you move, plan ahead if you want to make a quick jaunt into the ether, you might not make it back.
A space suit will protect you completely from coldness.
If your corpse is exposed to cold temperatures for too long, your body will freeze over, turning you unrecognizable. This is very useful for changelings to help disguise their killings.
Coffins and lockers provide some protection from the coldness of space. If you're lucky, your murderer will stuff you into one before launching you out of a mass driver, giving you time to call in and report the attack.
A fire extinguisher will blast whoever it's pointed at with cold water.