I am going to a wedding this sat in Saranac Lake NY for a 1pm outdoor/indoor wedding. I am torn between wearing a blue suit or grey pants w/ a dark blue plaidish blazer (which is light in weight) I assume it will be very warm out.
My suggestion is to go with the suit that is most comfortable and weather appropriate. Since you mentioned that the gray pants and dark blue plaid-ish blazer is light weight, that might be your best bet. Considering mother nature, the sun has been strong and very hot, so I would make sure that you are in a light material.