Today, malaria claims 90% of its victims in Africa, so people tend to think of it as a tropical disease.
But both the parasite that causes malaria, and the mosquitoes that transmit it, can survive over large swathes of the planet, and until recently, malaria regularly killed people all over the world.
In fact, the disease got its name relatively far from the tropics - Italians called it "mala-aria,"or "bad air," because they thought it was caused by noxious fumes emanating from swamps.
But Europe no longer has malaria.
Nor do other temperate places, including North America, Australia, and northern Asia.
That's partially because temperate countries developed more quickly - as people drained wet areas for agriculture, mosquitoes lost their breeding grounds.
And, as people gained wealth, they spent more time inside, where mosquitos couldn't reach them as easily.
But climate also helped, because, once the parasite spreads from a person to a mosquito, it needs time to develop into its infectious stage before getting transferred to another human.
The cooler the weather, the more slowly it develops, and under about 15 degrees Celsius, it can't reach its infectious stage at all.
So in temperate climates, fewer mosquitoes end up carrying the infectious form of the parasite than in the tropics, and, as a result, eradicating malaria has just been easier to do in temperate places.