weather · noun U /ˈweð.ər/Full view
weather
A1 the conditions in the air above the Earth such as wind, rain or temperature, especially at a particular time over a particular area
Dictionary examples:

bad/good/cold/dry/hot/stormy/warm/wet weather

The weather in the hills can change very quickly, so dress in layers.

We're going to have a picnic, weather permitting.

Learner example:

I need it because the weather is cold. (Key English Test; A2; Spanish)

be/feel under the weather
C2 to feel ill
Dictionary example:

I'm feeling a little under the weather this morning.

Learner example:

Why do we listen to music every time we are under the weather? As far as I am concerned, music plays a key role in my life. (Certificate of Proficiency in English; C2; Greek)

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