When there's weather that's annoying or uncomfortable, you want it to stop. In this case, you can use the phrase "let up":

When will this heat let up? My God, it's scorching!

When a person is nagging or criticizing you, you can ask them to "let up":

A: How many times do I have to ask you to throw away your empty bottles after you're done with them?

B: Will you let up? I'm doing something important here!