Yes, it will most likely be cold. Please bring a jacket/layers just in case. The barn where the ceremony + reception will be is fully heated and cooled, but there will be about 30 minutes when the barn will be flipped from ceremony to reception. During that time, guests will not be allowed in the barn and will either be outside in the courtyard, in their cars, etc.
No, but other pants are welcome :) -Khakis, slacks, etc.
-For the ladies, dresses are not required but are certainly a good option! Dress pants and a blouse are also perfectly fine. Whatever you decide, please be modest. -For the men, polos and slacks/khakis are great! Or, go for the dressier clothes, if you're feeling fancy.