crater lake is in klamath county. the lake is about northwest of the county seat of klamath falls, and about northeast of medford. the lake has an average depth of . its maximum depth is . the depth changes slightly as the weather changes. on the basis of maximum depth, crater lake is the deepest lake in the united states. it is the second deepest in north america, after great slave lake in canada. crater lake is also the ninth deepest lake in the world.