Plan on a range from high 50s to mid 70s. Last year at this time, it was in the 80's - so it could be hotter. I'll update as we get closer.
Think fun garden party! Jon isn't bringing a tie - so no need for full on suits for the men - unless suits and ties are your thing. The dinner on Saturday night will be causal - slacks and a fun shirt for the men, casual dress for the ladies or fun pants and blouse. The wedding will be like a dressy but casual garden party.