I was in Cancun July 1st-5th this past summer and it was HOT. Like, absurdly, uncomfortably, ridiculously hot. I (and my wedding coordinator) wouldn't recommend a date in June unless it is one of the first two weekends. My original date was Memorial Day weekend 2013, and she thought at would be perfect. (We pushed it back though to Nov because my sister is pregnant and due in May!) I just got back from a second trip to Riviera Maya this past Wednesday, and the weather was great; the only drawback was that it started getting dark really early We will likely have to start the ceremony at 3:30pm to ensure we have the right light for photos after the ceremony. My WC also said January-March are not ideal because even though the weather isn't cold (chilly at night, but not COLD), it can be very, very windy... Who knew?? April- early June, and late Oct-Dec are best. If you do any earlier than mid-Oct, there is a risk of hurricane.