The Extreme (Animorphs #25)

Marco and the other Animorphs have managed to find out where the Yeerks are planning to build their next ground-based Kandrona. That's a good thing. But the location is supposed to be somewhere near the North Pole. That's a bad thing. The Animorphs know that the Yeerks are a "cold-blooded" species, but this is a little nuts! Who wants to be near the North Pole without Arctic morphs -- and wearing spandex?Even so, the kids know that if the Yeerks succeed with their plan, Earth is pretty much done