Cancún in May is pre-rainy-season Caribbean — 31°C / 88°F afternoons, 23°C / 73°F nights, the calmest beach month before June's first thunderstorms arrive.
Cancún in May runs Caribbean pre-rainy-season heat. Servicio Meteorológico Nacional (SMN) data put afternoons at 31°C / 88°F and overnight lows at 23°C / 73°F with 6 rain days, calmer than the June-October rainy season. Humidity holds at 80%. The Hotel Zone (Zona Hotelera) — the 22-kilometer barrier strip of all-inclusive resorts — runs an enforced resort register: cover-ups required over swimsuits in restaurants and lobbies, smart-casual at dinner. Downtown Cancún (El Centro) is everyday Mexican: cotton dresses, linen trousers, leather huaraches. Mayan-Yucatán heritage runs through the textile vocabulary; the white huipil dress with embroidered yoke is sold across Mercado 28, and Pineda Covalín produces the silk-printed scarves citing Mexican folk-art motifs. Reef-safe sunscreen is required at every cenote and at Xcaret-Xel-Há eco-parks. Aldo Conti and Pineapple Republic carry the resort-shirt vocabulary; Yucateco-cotton from Mérida brands like Coqui Coqui sets the upmarket register.
Cancún May is the last calm month before the rainy season — 31°C / 88°F water glass-flat at Playa Delfines, the resort restaurants still closing at 11pm, the Mayan-Yucatán palette holding white-cotton-and-bone-sandal across every Hotel Zone lobby.

31°C / 88°F afternoons + 80% humidity require breathable fibers; synthetic activewear traps sweat in the Caribbean climate.

Resort-restaurant smart-casual at Hotel Zone dinners (La Habichuela, Lorenzillo's, Harry's). Linen breathes through the 23°C / 73°F evening.

Cenote and Mayan-ruin (Tulum, Chichén Itzá, Cobá) day trips — UV index 11; Yucatán sun is sharper than the latitude suggests.

Beach-to-pool-to-restaurant transitions; closed-toe required at evening restaurants. Skip flip-flops past the swim deck.

Mexican resorts enforce cover-ups over swimsuits in lobbies and restaurants. Skip going topless or string-bikini-only into resort interiors.

UV index 11 daily; the Caribbean reflection at Playa Delfines doubles exposure. Polarized cuts the glare.

Mercado 28 and Mercado 23 are documented pickpocket zones; diagonal-worn bag stays in front.

Quintana Roo restricts oxybenzone-based sunscreens at cenotes (Cenote Ik Kil, Cenote Dos Ojos), Xcaret, Xel-Há, and the Mesoamerican Reef. Mineral-only enforced.
Cotton midi dress · sandals · sun hat · crossbody · reef-safe SPF. Beach 8am at Playa Delfines (Punta Nizuc end), breakfast at Hotel Zone resort, snorkel at Garrafón 11am.
Linen trousers · cotton shirt · leather sandals · light cardigan. Dinner at La Habichuela (downtown) or Harry's (Hotel Zone) 8pm; cocktails at Coco Bongo or Mandala after.
A suggested look — Cancun May suggested look: white linen kaftan midi dress, cognac huarache sandals, jipijapa palm hat, tortoise sunglasses, and no handheld extras for Playa Delfines morning..
Per Servicio Meteorológico Nacional (SMN): average daily high 31°C (88°F), low 23°C (73°F), 6 rain days totalling 90mm. Humidity holds at 78-82%. May is the last pre-rainy-season month — the rainy season runs June through October with the heaviest rainfall in September-October during Caribbean hurricane season. UV index sits at 11 (extreme) all month; daylight 13 hours.
Yes — Quintana Roo state law restricts oxybenzone and octinoxate sunscreens at every cenote (the underground freshwater pools), at Xcaret and Xel-Há eco-parks, and across the Mesoamerican Reef snorkel zones. Bring zinc-oxide-based mineral SPF 50 (Stream2Sea, Sun Bum Mineral, Thinksport are widely cited reef-safe brands). Mexican pharmacies and resort shops sell reef-safe options at higher prices than US importing.
Smart-casual: linen trousers or a cotton midi dress, leather sandals or loafers (no flip-flops past the pool deck), a light cardigan or button-down for the 23°C / 73°F evening. Hotel Zone restaurants (La Habichuela, Harry's, Lorenzillo's, Puerto Madero) enforce a cover-up over swimsuits and closed-toe shoes at dinner. The Mexican dining hour runs late — most kitchens stay open till 11pm or midnight.
Yes — May has fewer rain days than the June-October rainy season, water levels stay clear, and the morning crowds at Cenote Ik Kil, Cenote Dos Ojos, and Gran Cenote (Tulum) are smaller than peak winter. Pack: reef-safe SPF, water shoes (cenote rocks are sharp), quick-dry towel, cotton cover-up. Skip oxybenzone sunscreen; rangers at Ik Kil and Xcaret check.
Pineda Covalín for silk-printed scarves citing Mexican folk-art motifs; Aldo Conti for resort menswear (multiple Cancún locations); Pineapple Republic for beach kaftans and cotton resort-wear; Coqui Coqui (Yucateco upmarket) for cotton kaftans and natural-fiber resort dresses; Mercado 28 for handmade Yucatán huipil dresses with embroidered yokes; Coqueta for resort-luxury swimwear. The Mayan-Yucatán heritage textiles — handwoven cotton, embroidered tunics — are the most distinctive local register.