What this solves
Portugal's Atlantic coast is colder than the Mediterranean equivalent — a July water temp of 19–21°C is a "you can swim" experience, not a "bath" experience. The Algarve runs a touch warmer (21–22°C in August, sheltered by Cape São Vicente), the Lisbon / Cascais coast at 19–20°C, and the Azores sees 22°C in summer 14°C in winter. Air temperature lies; people wade into 16°C water expecting the bath-like Mediterranean and come out shivering.
This tool tells you the typical sea temperature for a given month and place, plus the wetsuit suggestion that matches a real cyclist's endurance.
Pick month & location
Adjust inputs. Tool shows water temp and wetsuit suggestion.
How to read the result
- Water temp is the typical reading for the month and place — not a single-day value. Real temps vary ±1.5°C with weather and tide.
- Wetsuit is a suggestion based on activity duration and cold tolerance. It assumes neoprene thickness.
- A 3mm shorty = sleeveless, shorts only. A full 3mm = arms and legs covered. Below 16°C, plan on a full suit for any 30+ min session.
- Air temperature lies. A 28°C August afternoon does not make the water bath-like. The Atlantic coast is colder than most visitors expect.
Monthly sea temperature reference (°C, 2026)
Indicative values from IPMA + NOAA + Climate-Data.org. Actual varies ±1.5°C.
| Month | Algarve (S) | Cascais | Setúbal | Nazaré | Porto | Costa Vicentina | Azores (S. Miguel) |
|---|---|---|---|---|---|---|---|
| January | 16 | 15 | 15 | 14 | 14 | 15 | 17 |
| February | 16 | 14 | 14 | 14 | 13 | 14 | 16 |
| March | 16 | 15 | 15 | 14 | 14 | 15 | 16 |
| April | 17 | 16 | 16 | 15 | 14 | 16 | 17 |
| May | 18 | 17 | 17 | 16 | 15 | 17 | 18 |
| June | 19 | 18 | 18 | 17 | 17 | 18 | 20 |
| July | 20 | 19 | 19 | 18 | 18 | 19 | 22 |
| August | 22 | 20 | 20 | 19 | 19 | 20 | 22 |
| September | 22 | 20 | 20 | 19 | 19 | 20 | 22 |
| October | 21 | 19 | 19 | 18 | 18 | 19 | 21 |
| November | 18 | 17 | 17 | 16 | 16 | 17 | 19 |
| December | 17 | 16 | 16 | 15 | 15 | 16 | 18 |
Wetsuit suggestion by activity
| Water temp | Casual swim | Snorkel (30–45 min) | Surf / kayak (1–2 hrs) |
|---|---|---|---|
| ≥ 22°C | None | Rash guard only | Boardshorts / rash guard |
| 20–21°C | Optional 2mm shorty | 2mm shorty | 3mm shorty |
| 18–19°C | 3mm shorty | 3mm shorty | 3mm full |
| 16–17°C | 3mm full | 3mm full | 3mm full + booties |
| ≤ 15°C | 3mm full + booties | 4mm full | 4/3mm full + hood |
Limitations
- Water temp varies with weather, tide, and upwelling. Coastal upwelling events in July–August can drop the Lisbon coast to 14–15°C for days at a time.
- The figures here are surface-level. Deeper water runs cooler; wreck divers and spear-fishers often bring 5mm suits even in summer.
- The Azores figures are for São Miguel. The western islands (Faial, Flores) are slightly cooler.
- This tool assumes you can swim. Non-swimmers should not rely on cold-tolerance tips — use a flagged beach with lifeguards.
FAQ
Is the Algarve warm enough for kids in May?
Air is warm (24°C), water is 18°C — most kids tolerate it but a 30-min swim is a stretch. Plan a beach with a tide pool (Tascent lagoon in Ria Formosa) for non-swimmers.
When is the Algarve truly "bath-like"?
August–September. The water climbs to 22°C, the air is 28–32°C, and a 45-minute session is comfortable. May–June is 18–19°C — bath-like only briefly.
Do I need a wetsuit for surfing in the Algarve?
3mm full suit for June–October. In July–August, a 2mm shorty is borderline. In summer (low Am), Aquastores rent by the day at ~€10–€15.
Is the Azores warmer than the mainland?
Yes, by 1–2°C in summer (22°C) and 2–3°C in winter (17°C). But the trade-off is the swell: bigger and more consistent than the Algarve. Bring a thicker suit.
Related tools
Match swim-month to crowd-month — May and October are the sweet spots.
Costa Vicentina vs AlgarveThe Costa Vicentina runs 2–3°C colder than the south. Wetsuit math.
Algarve cave tour pickWetsuit months for kayak tours; wetsuit included in price.
Azores whale seasonWhale-watching sea state by month — the same data, but for boats.
Sources & methodology
- IPMA — Instituto Português do Mar e da Atmosfera — coastal sea-temperature buoys.
- NOAA — National Oceanic and Atmospheric Administration — Atlantic sea-surface temperature archive.
- Climate-Data.org — long-term monthly averages for coastal stations.
- Local surf-school wetsuit-hire data, summer 2024–2026, for Algarve, Cascais, Ericeira, Azores.
- Hydrographic Institute (Instituto Hidrográfico) — Portuguese Navy coastal sea-state reports.