Hotel rates can drop on the Caribbean Coast by as much as 50% in the low season (September to approximately mid-December). In high season, however, it's virtually impossible to find low rates, especially in Playa del Carmen. During Christmas week, prices can rise as much as $100 a night—so if you're planning a Christmas vacation, you'd do well to book six months in advance.
Keep in mind that visiting during a traditional festival such as the Day of the Dead (which culminates on November 2 after three nights of candlelit ceremony) can be more expensive—but it can also be an unforgettable experience.
From November to April, the coastal weather is heavenly, with temperatures hovering around 80°F and near-constant ocean breezes. In July and August, however, the breezes disappear and humidity soars, especially inland where temperatures often reach the mid-90s. September and October bring the worst weather: there's often rain, mosquitoes, and the risk of hurricanes.