Due to his radiation powers, Derek Powers/Blight (Batman Beyond) is resistant to extreme cold, able to shrug off shots from Mr. Freeze's ice guns and being thrown in an icy river without getting cold.
Superman (DC Comics) is resistant to heat and cold.
Supergirl (DC Comics) is resistant to heat and cold.
Broly (Dragon Ball series) possessed such power that he was able to survive the lethal heats of molten magma unscathed with his barrier; only the nuclear heat of the sun was able to kill him.
Thanks to the Robe of the Fire-Rat, Inuyasha (InuYasha) can withstand exposure to extreme heat and open flames.
Link (Nintendo), when donning a Goron's Tunic, is immune to volcanic heat.
The Hulk's (Marvel Comics) impenetrable skin is resistant to heat.
Skaar (Marvel Comics), born in a volcano, is resistant to heat.
Benjamin Grimm/The Thing's (Marvel Comics) impenetrable skin is resistant to heat.
The Human Torch (Marvel Comics), composed of fire, is immune to heat.
Iceman (Marvel Comics) is immune to cold.
Crystalia Amaquelin/Crystal (Marvel Comics)
Solara (Marvel Nemesis: Rise of the Imperfects) is fireproof.
A Flame Human, Portgas D. Ace (One Piece) is immune to heat.
A Sand Human, Crocodile (One Piece) is immune to desert heat.
An Ice Human, Kuzan/Aokiji (One Piece) is immune to cold.
A Lava Human, Sakazuki//Akainu (One Piece) is immune to heat.
Don Accino (One Piece), regulating his own temperature, is immune to heat and cold.
Rhydon's (Pokémon) impenetrable skin is resistant to heat.
Due to his power over water, Percy Jackson (Percy Jackson and the Olympians) is highly resistant to heat, even being able to survive being submerged in magma.
Tyson (Percy Jackson and the Olympians) is resistant to heat, just like every other cyclops.
Thanks to having very thick fur, the Mamuts (Serious Sam) can adapt themselves within cold regions as well as from cold precipitation like rain, especially the arctic variants that are located on the Ice Planet.
Garnet (Steven Universe) is immune to extreme heat or cold, ranging from scalding hot coffee to molten lava.
Bismuth (Steven Universe) is immune to lava, handling lava and red-hot metal with her bare hands with no ill effects.
Bowser (Nintendo) is resistant to heat to the extent that he has survived being submerged in lava on multiple occasions.
The Fireborn (Turok) has been genetically and magically conditioned to be heat-resistant, able to even walk through molten lava without harm.
Kelvin (Valkyrie Crusade) is not affected by virtually any temperature, not even by the absolute zero.
Hiei (Yu Yu Hakusho), being a fire-and-ice demon, is immune to both heat and cold.
Adam, Bree, and Chase (Lab Rats) are more suited to handle extreme climates that are extremely hot or cold for a normal human.
Nuova Shenron (Dragon Ball GT)
Hot Shot (Ben 10 Reboot)
Pyronites (Ben 10) like Heatblast is resistant to heat and cold.