Beach destinations in May
Regions we have researched where the sea is typically comfortable in May, and regions where it usually is not. These are climate averages for one reference town per region, not a forecast, and conditions change along any coast.
Typically warm enough for swimming (5)
Spain
Canary Islands
Typical sea temperature in May: about 20 °C (one reference town)
Sea is 18-24 C all year, warmest September-October; source recommends May to mid-October with August-October best for swimming. North coasts are cloudier and windier (trade winds); the south and west coasts are sunniest and driest. Sun is strongest late May to late July.
NE trade winds up to about 50 kph in afternoons; calima (hot Saharan dust wind) most frequent July-August, especially on eastern islands. Values shown are Tenerife South; Lanzarote/Fuerteventura are 1-2 C cooler in winter and summer.
Thailand
Gulf of Thailand - Koh Samui
Typical sea temperature in May: about 30 °C (one reference town)
Wettest months are October to December, November the peak at about 445 mm; the island is drier from mid-January to April and rains in May-September mostly as short showers. Sea is 28-30 C all year.
Heavy rain October-December; rain-days peak at 16 in Oct and Nov.
USA
Florida Gulf Coast (Tampa Bay to Pensacola)
Typical sea temperature in May: about 25 °C (one reference town)
Gulf water is 25-30 C from May to October and drops to about 19-20 C in winter (Tampa), colder at Pensacola (17.5 C in February). May is described as generally excellent with fewer thunderstorms than summer; summer brings near-daily storms and humidity.
Hurricane season June-November, highest risk August-October. Red tide (Karenia brevis) blooms are most common late summer to winter, mainly between Clearwater and Sanibel Island; FWC lists the highest-occurrence months as September-January.
USA
Florida Atlantic Coast (Miami to Jacksonville)
Typical sea temperature in May: about 27 °C (one reference town)
Miami water stays 23.5-30 C all year, but the source says December to April is the best overall period and mid-March to late April best for swimming since winter can be cool and windy. May to October is the wet season with daily showers and storms. Northeast Florida water is cooler in winter (21 C).
Hurricane season June-November, more frequent August-October.
USA
Hawaii
Typical sea temperature in May: about 25 °C (one reference town)
Sea is 24-27 C all year, so swimming is possible year-round. Best time to visit per source is May to October when trade winds ease the heat; exposed north-facing coasts get higher waves and brief winter storms occur December to March.
Hurricane/cyclone season June-November, August-September most likely though direct hits are rare. Winter surf on north-facing shores is only implied by the source (higher waves on exposed coasts) - verify with local lifeguard authorities. Honolulu values shown.
Usually cooler in May (24)
Greece
Crete
Typical sea temperature in May: about 19 °C (one reference town)
Warm swimming sea from about June to October at Heraklion, peaking in August. The northwest meltemi wind blows from mid-May to mid-September; rain falls mostly October to March.
Meltemi wind mid-May to mid-September per source; sea state on exposed coasts not assessed.
Greece
Cyclades (Santorini, Mykonos, Naxos)
Typical sea temperature in May: about 18.5 °C (one reference town)
Sea reaches about 24 C in August and stays cooler than the Ionian because the meltemi stirs the water. Wind can start in May and may make sea conditions rough even on sunny days. Rain is rare April to September.
Meltemi spells of a few days to weeks, strongest July-August, usually ending by October per source.
Greece
Ionian Islands (Corfu)
Typical sea temperature in May: about 18.5 °C (one reference town)
Warmest of the Greek sea tables fetched except Rhodes, about 26 C in August. Summer is nearly rainless but autumn is wet (December 195 mm, November 175 mm at Corfu). First half of September often still good.
Wet autumn and winter; occasional cold windy days in winter per source.
Greece
Rhodes and the Dodecanese
Typical sea temperature in May: about 20 °C (one reference town)
Warmest Greek sea in the fetched data, about 26.5 C in August and still 23.5 C in October. Beach window June to mid-September; early June evenings can be cool. Meltemi reaches the Aegean from mid-May.
Rain concentrated October to March.
Italy
Sicily
Typical sea temperature in May: about 18.5 °C (one reference town)
Palermo sea is 25-26.5 C July to September; June still cool, early September good, bad weather creeping in late September. Scirocco heat spells can reach 40-45 C in summer. Rain peaks in autumn and winter.
Scirocco heat waves June-August (up to 43-45 C at the hottest).
Italy
Sardinia
Typical sea temperature in May: about 17.5 °C (one reference town)
Porto Cervo sea is 24-25 C July to September, a bit cool in June and October; slightly cooler on the west. The maestrale (northwest wind) hits the west and the Strait of Bonifacio and the island is windiest October to April.
Maestrale wind, mainly west coast; early autumn weather can turn from mid-September.
Italy
Campania (Naples, Amalfi Coast, Cilento)
Typical sea temperature in May: about 18.5 °C (one reference town)
Naples sea reaches 25.5-27 C in July-August; June is still a little cool. Autumn is the wettest season (November 160 mm). Page does not cover Amalfi specifically; figures are for Naples.
Italy
Puglia (Apulia)
Typical sea temperature in May: about 18 °C (one reference town)
Bari sea is 25-26 C in July-August; June still cool, September quite warm but weather can break in the second half. Salento is described as windy. Cold Balkan air can bring snow in winter.
Italy
Liguria (Italian Riviera)
Typical sea temperature in May: about 18 °C (one reference town)
Genoa sea tops out about 25 C in August, 24 C in July, 22.5 C in September. July-August is best per source. Autumn brings heavy rain (October 170 mm) that can cause flooding; the western Riviera is drier than the central-eastern coast.
Autumn flooding rain, especially September-November.
Portugal
Algarve
Typical sea temperature in May: about 18 °C (one reference town)
South-coast sea peaks around 21.5 C in August and September at Faro, so water stays on the fresh side. Beach window June to mid-September; wind blows often (April windiest on average) and evenings can be cool. Rain October to March.
Frequent wind; cooler sea on the exposed west of the Algarve (Sagres) is mentioned qualitatively with no figures.
Portugal
Lisbon and Estremadura west coast
Typical sea temperature in May: about 17 °C (one reference town)
Atlantic water is clearly cool even in summer: about 20.5 C in July-August at Lisbon, 15 C in winter. Source suggests mid-April to mid-June and mid-September to early October for visiting; summer winds are strongest in July-August.
Wettest November-January; windy in July-August (average 17-18 kph) and winter westerlies.
Portugal
Madeira (incl. Porto Santo)
Typical sea temperature in May: about 19 °C (one reference town)
Sea 22-24 C from July to October, never below 18 C. Summer is the sunny season; the south coast around Funchal is sheltered while the north is windier.
Leste (hot Saharan wind with dust) possible June-October; rain and Atlantic depressions October to mid-April.
Portugal
Azores
Typical sea temperature in May: about 18 °C (one reference town)
Sea reaches only 22-23 C in July to September and about 16-18 C otherwise. Summer is drier but still has 5-7 rainy days a month; autumn and winter are wet and stormy, especially on the northwest islands.
Wind storms November-March; weakened hurricanes occasionally arrive, mostly September-October (Ponta Delgada figures shown).
Spain
Costa del Sol (Malaga)
Typical sea temperature in May: about 17 °C (one reference town)
Sea peaks about 23 C in August, cooler than the rest of the Mediterranean because Atlantic water enters. Source gives June to mid-September as the beach window. The terral, a hot dry wind from inland, can push summer heat up.
Terral wind in summer; rain October to March.
Spain
Balearic Islands (Mallorca)
Typical sea temperature in May: about 17 °C (one reference town)
The Mallorca page lists sea about 24 C in July, 26 C in August, 24 C in September; June (21 C) and October (22 C) are cooler. Best window per source June to mid-September. The island is windy October to April, and October is the wettest month.
Autumn rain and winter wind; the source does not name specific winds.
Spain
Costa Brava (Catalonia)
Typical sea temperature in May: about 17 °C (one reference town)
Lloret de Mar sea is 23.5-25 C July to September, 20.5 C in June, 17 C in May. Source suggests mid-June to August for the beach, May, June and September for sightseeing away from peak heat. Autumn is the rainiest, October the most.
Autumn heavy rain; the source does not mention the tramontana wind.
Thailand
Andaman coast (Phuket, Krabi)
Typical sea temperature in May: about 30.2 °C (one reference town)
Dry season roughly December to March. Southwest monsoon May to October brings heavy rain (Krabi October about 325 mm) and rougher seas with dangerous currents. April is hot with pre-monsoon showers; early November can still be very wet.
Rough sea and dangerous currents in the monsoon; west-facing beaches get higher waves June-September. Seasonal boat/tour reductions plausible but not documented in sources fetched.
Thailand
Eastern Gulf (Pattaya area)
Typical sea temperature in May: about 30.5 °C (one reference town)
Dry season December to April; rainy May to mid-November with September-October heaviest. Source prefers December to mid-February before it gets hotter. Sea 27.5-30.5 C year-round. Pattaya is used as a proxy; islands like Koh Chang were not assessed.
Türkiye
Antalya and the Turquoise (Mediterranean) Coast
Typical sea temperature in May: about 20.5 °C (one reference town)
Warmest Turkish sea in the data, 27-28 C in July to September. Source calls July-September most pleasant, June and October warm enough, May and November only cool. Summer highs average about 35 C and heat waves can exceed 40 C; June and September are suggested to avoid peak heat. Rain is heavy December-January.
Summer heat waves (record high 45 C). Kas and Fethiye are not separately sourced; Antalya values are used for the whole Mediterranean coast.
Türkiye
Bodrum and Aegean Coast
Typical sea temperature in May: about 19 °C (one reference town)
Cooler sea than the south coast, about 23.5-24.5 C July to September; source calls August warm enough for swimming and July/September barely acceptable. The meltemi north wind blows in summer. Summer is very hot (July highs about 34 C, heat waves 40 C or more); winter is wet.
Meltemi wind in summer; heat waves.
Türkiye
Marmaris and the Southwest Coast
Typical sea temperature in May: about 20 °C (one reference town)
Sea 25-26.5 C July to September, between Bodrum and Antalya. Summer is very hot, with a record 45 C in August 2021. The page does not say whether the meltemi reaches Marmaris. Winter rain is heavy (December 290 mm).
Heat waves; Fethiye/Dalaman, Datca and Dalyan were not separately sourced.
Türkiye
Black Sea Coast (Trabzon, Samsun, Rize)
Source says Trabzon sea is warm enough July to September at about 26 C in August; the northeast (Rize) has frequent heavy summer rain and limited sunshine. Samsun's bay is relatively sheltered. Weather is less reliable than on the south coast.
Frequent summer rain, especially northeast; only August sea temperature available.
USA
Southern California
Typical sea temperature in May: about 17 °C (one reference town)
Pacific water is cool: 19.5-20.5 C even at its warmest in San Diego, 15-16 C in winter. Source gives July to October as best for the beach. Morning fog (June gloom) hits mostly May and June, occasionally July.
Coastal morning fog May-July; water temperatures north of San Diego are not covered by the source.
USA
Cape Cod and New England
Typical sea temperature in May: about 9 °C (one reference town)
Atlantic water is cold: Boston is about 18.5-20 C in July-August and under 10 C from December to May. NPS says Cape Cod National Seashore summer water averages 60-70 F (about 16-21 C), with early July around 55-60 F at Marconi Beach in a 2016 notice.
NPS lifeguards at Cape Cod National Seashore beaches typically late June to Labor Day only; shark activity noted into September-October. Boston values shown (not Cape Cod itself, which is cooler on the open-ocean side).
Swim months are derived from monthly sea-temperature tables (about 22 °C and above) plus the source’s stated best window. Crowd levels are not covered. Sources are listed on each destination page.