Under the weather

To say that someone is "under the weather" is to say that they are not feeling very well.
Example: "What's wrong?" Answer: "I'm a bit under the weather." They probably have a simple cold or flu which will go away quickly. Example: "It's nothing serious; I'm just a bit under the weather." Being "under the weather" reminds us that a quick change in the weather can affect our health and the way we feel.