Bad weather only half rare during autumn (8)

I believe the answer is:

rainfall

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'bad weather' is the definition.
'rainfall' can be an answer for 'weather' (rainfall is a kind of weather). I am unsure of the 'bad' bit.

'only half rare during autumn' is the wordplay.
'only half' indicates taking half.
'during' becomes 'in' (e.g. during February means in February).
'autumn' becomes 'fall' (synonyms).
'rare' with half the letters taken is 'ra'.
'ra'+'in'+'fall'='RAINFALL'

Can you help me to learn more?

(Other definitions for rainfall that I've seen before include "Precipitation, get out umbrella" , "Form of precipitation" , "Water falling in drops" , "Shower" , "Amount of water coming down" .)

I've seen this clue in The Times.

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