Heat Wave is a mythos card. It first appeared in the Arkham Horror board game.
Mythos Type: Environment (Weather)
Gate Opens: Woods
Clue Appears At: *Independence Square
Mythos Ability: Fight checks in Arkham are made at a -1 penalty. Lore checks in Arkham are made at a +1 bonus. Fire Vampires have their toughness increased by 1.