What kind of dress is appropriate for a summer wedding?

It's fine to wear the same thing to both as long as you remember one rule-- it's the bride's day so make sure you don't overshadow her and her dress! For June you can get by with a trendy flower print with spaghetti straps as long as you have a scarf or shawl for the church (no bare shoulders in church!) You will be fine in just about anything, just again make sure you don't take the attention away from the bride. Have fun!