Vampires in fiction are almost always colder than they were before they turned. This most likely originates from the fact that vampires are essentially living corpses, or it may be due to evil being cold. Of course, having Friendly Neighborhood Vampires in the setting would probably mess with that analogy.
Another problem with this trope is that there's no reason a dead (or undead in this case) thing would be abnormally cold. When someone says a dead body is "cold," they really mean "colder than I know a human body should be." Without some extra bit of magic, dead (or undead) things should be room temperature at best. Sometimes they even heat up to higher than room temperature because of the energy released in the breakdown of the body during decomposition.
Please note that vampires aren't the only undead with Cold Blood, they're just the most commonly used examples. Any undead creature with an abnormally cold temperature counts as well.
- In The DCU, supervillain Kobra killed his brother Jason's girlfriend, then resurrected her as a zombie and sent her to kill him. Jason's last words were as he embraced her, remarking that her skin was as cold as ice. This sentence trailed off as realization dawned on him just before the zombie stabbed him in the back and threw him from the cable car.
- Vampires: Los Muertos actually shows the vampire's body as being blue through a heat sensing goggles-type thing.
- Invoked in The Sookie Stackhouse Mysteries (and by extension, True Blood). At one point in the books, Sookie becomes intimate with a non-vampire for the first time and notes how strange it is to have sex with a warm body.
- Twilight vampires are physically cold and "marble-like". The werewolves, by contrast, have a higher-than-average body temperature.
- In New Amsterdam by Elizabeth Bear (the book, not the TV show), Sebastian, resident Spanish wampyr detective, is cold and doesn't have free-flowing blood in his body.
- Inverted with the "vampires" of I Am Legend, who are humans with a disease that (among other things) sends the body into overdrive. They run a fever of about 103 Fahrenheit as a baseline.
- A Song of Ice and Fire:
- The Others, undead and cold, to the point where the ambient temperature drops when they're around.
- The wights, the reanimated corpses of the Others' victims are also ice-cold to the touch, though they don't drop the ambient temperature.
- American Gods teaches us that while the undead may not be colder than room temperature, they feel so cold that experiencing any other sensation at all becomes a problem.
- The Archancellor's hat from Discworld seems to contain the souls (or shades) of all the previous archancellors. It can deliver a freezing chill from within because of it.
- The zombies in Galaxy of Fear: City of the Dead are very cold. Doctor Evazam has one of them hold a "patient" down to immobilize him, in lieu of conventional straps, and Zak finds his hands icy and impossibly strong.
- In Bloodsucking Fiends, vampires' lack of body heat is a plot point: they can identify each other by sight with their heat-based Aura Vision, and one human singles Jody out as a supernatural entity by spying on her with infrared goggles.
- In Buffy the Vampire Slayer, The Initiative discovered that a vampire (specifically Spike) was in Willow's dorm room because their Infrared Xray Camera read him as only slightly above room temperature.
- Ghosts in Supernatural cause the temperature to drop.
- As in the books, the temperature around the White Walkers drops notably in Game of Thrones, to the point that fires next to them are extinguished.
- Liches, undead spell casters in Dungeons & Dragons, have a touch that can inflict cold-based damage.
- One particularly nasty Elite Zombie is the Bleakborns, also known as Moil Zombies. They look like normal zombies, with one important detail: frostbites and other ice-induced wounds on the corpse that won't disappear even in hot environments. These monstrosities have a heat-draining aura, dealing cold damage to everyone in it while healing them. And if you try to burn them? They eat the flames.
- Vampires in Vampire: The Requiem don't have any body heat by default, although they can expend some of their blood reserve to fake a metabolism for a short time. It's mentioned that, even though vampire blood is a potent Fantastic Drug, the sheer awfulness of drinking sludgy room-temperature blood is a serious obstacle to consumption at first.
- In Vampire: The Masquerade Bloodlines, this is how your character is identified as a vampire: you don't show up on the heat scanners.
- Also a feature of Vampires in the tabletop game, Vampire: The Masquerade actually warns players that they should keep this in mind while human hunters are around, especially in cold weather, as it will give them away. Additionally the game has the Naga, weresnakes that can alter their physiology to go cold blooded, and grow their snake fangs, allowing them to pass for Vampires in some circumstances.
- The Scourge are covered in frost and blue glow, and their spellcasters have entirely cold-based powers. It may have more to do with their origin than any law of the undead though - they hail from Northrend and their master The Lich King sits on The Frozen Throne. Unaffiliated undead are just as likely to use fire or lightning magic than they are to use frost.
- Playable Death Knights in World of Warcraft can play this straight by building into Frost. However, their other talent trees, Blood and Unholy, mostly avert this.
- When Bolvar Fordragon became the new Lich King, the Scourge remained frost-based. The Lich King himself gained some fiery abilities, however.
- Most undead in Dominions are associated with cold and resistant to it, and some are even surrounded by chilling auras.
- Ethreain the Lich from Dota 2 is based on Kel'Thuzad from Warcraft (in the original Defense of the Ancients: All-Stars, he was him). He comes with ice spells... and plenty of ice puns.
- Zombies in Earthbound can use their arctic-cold breath to inflict the Cold status.
- In The Order of the Stick, when Malack is outed as a vampire, he says he rather thought that it was obvious, given his lack of body heat. Durkon responds that he just figured that Malack, as a lizard-folknote , was cold-blooded. "Actually, when active, exothermic organisms like lizards have comparable body temperatures to—" "I dinnae want a science lesson right now!"
- Adventure Time: "Aren't you cold, Finn?"