1. It's usually very windy and foggy.
2. It's usually very windy and it's very foggy.
3. It's usually very windy and it's very foggy.
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Does #1 mean #2 and #3?
2 and 3 are identical, aren't they?
Yes, they mean the same as 1, but the extra words make them wordy.
I corrected two parts.
1. It's usually very windy and foggy.
2. It's usually very windy and it's very foggy.
3. It's usually very windy and it's foggy.
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Does #1 mean #2 or #3?
They still all mean about the same thing.
1 has a compound predicate adjective "windy and foggy" which is modified by "very."
2 and 3 have become compound sentences -- two shorter sentences in each, joined together by "and."
The only difference in 3 is that there must be a little less fog, since it's not "very foggy" anymore!