The most common and most likely answer to this crossword clue is the 5 letter word FOGGY
I've seen this crossword clue in The Guardian
F
O
G
G
Y
More clues leading to the result FOGGY
Buddy explains!

The straight part
We know that "bad weather" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bad weather = foggy.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does FOGGY mean?
FOGGY adjective- Obscured by mist or fog; unclear; hazy
- Confused, befuddled, etc.