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.