Well that depends on a lot of factors, the key ones concerning whether you’re attending a formal or informal ceremony and reception, in the daytime or in the evening.
Humidity is a given in July and August, so you’ll want to dress as comfortably as decorum allows (i.e., maybe the tube top sundress isn’t the best choice for a church ceremony).
And take plenty of tissues. There are sure to be rivulets of melting mascara to contend with, even if you don’t tend to cry at weddings.
According to theknot.com, you should dress for a daytime wedding as you would for any other social event held at about the same hour and during the same season.
For example, if it’s a spring brunch or luncheon, a pretty suit or floral dress would be appropriate for women.
These days, pants are fine, too, as long as they are “dressy” enough. The trendy palazzo pants have the added benefit of helping the wearer keep her cool, especially in a drapey, gauzy fabric.
Black is probably not a good idea for a daytime summer wedding. It doesn’t exactly seem as bright and sunny as a bridal bouquet, and besides, it will only make you hotter.
Likewise, theknot.com advises that considerate guests leave the white and ivory/cream shades to the bridal party.
For men, daytime weddings in the spring or summer call for light-colored suits. Consider linen or seersucker.
An invitation is your best cue as to whether an evening wedding is to be a formal occasion. If the location indicates a very formal wedding, cocktail dresses for women and darker suits (or tuxedos, if it’s a black-tie affair), for men are in order. Women can also choose a dressy suit or nice dress.
For evening weddings in summer, a nice, cool black dress can be perfect choice, especially if it’s in a classic style. Use your judgment.
For men, a formal evening wedding will require a tuxedo. “Black Tie” is often printed on the invitation, but you will not often see “White Tie” (which requires men to wear white vest, white shirt, and white bow tie, with tails). If this is the attire, it is usually spread by word of mouth.
Rachel Leitao, Your Big Day