S is for Space

Of course! We are one big, happy fleet! Ah, Kirk, my old friend, do you know the Klingon proverb that tells us revenge is a dish that is best served cold? [pause] It is very cold in space!
Khan, from Star Trek II: The Wrath of Khan (1982)

So, is it true that space is always cold?

Actually, you are asking the wrong question. Space is mainly empty - no air, no matter, nothing. It’s only when you put something in space, like an asteroid, a satellite, or even an astronaut, that you can measure temperature. If you're in total darkness at the coldest spot in the known universe, the vacuum of space can get down to -270.45 degrees Celsius (reportedly the temperature of the cosmic microwave background radiation, which permeates the entire Universe). Which is as cold as it can get.

However, in direct sunlight near Earth, temperatures can vary wildly. A piece of bare metal in space, under constant sunlight can get as hot as 260 degrees Celsius. This is obviously dangerous to astronauts who therefore take great precautions to protect themselves if they are called to carry out an EVA (extravehicular activity, or spacewalk). That's why astronauts wear reflective white spacesuits, complete with both heaters and cooling systems.