Here is what US rules say you are owed, and what they do not cover.
If the airline cancels and you decline the rebooking or a voucher. The cause, weather included, does not matter.
Federal rules do not require them for weather. Your card's trip-delay cover might pay.
20 calendar days if you paid by cash, check or debit.
A voucher is the airline's offer, not your right. See the full guide.