Welcome to English in a Minute.
Sometimes American English doesn't seem to make sense, like this:
"I am under the weather."
Under the weather -- what could that mean?
A: Are you okay?
B: Um, not really. I think I'm a little bit under the weather.
A: You should go home and get some rest.
B: Yeah, I think that's a good idea.
If you stand "under the weather," you might have a dark storm cloud over your head, and you might not feel very well.
When you say you are "under the weather," it means you are sick or not feeling well. This phrase comes from sailors at sea. If a ship was in a bad weather and its sailors were sick, the crew would go below deck, to get out from "under the weather" to try to feel better.
And that's English in a Minute.