Cancún & the Yucatán is in its storm season right now, June to November. Most trips are unaffected, but a storm reroutes flights and closes beaches at a day's notice — the packing consequence is a buffer day and a charged power bank, not different clothes.
Going in May
Nothing seasonal is running in May.
Packing for Cancún & the Yucatán?
Build a packing plan around the season you are actually travelling in.
Seasonal ranges are typical, not guarantees — a monsoon can arrive early and a dry season can break. Check the forecast before you seal the bag.