- Temperature
- Feels like
- Rain
- Wind
- Sea water
- Waves
- Updated
Sea water: 17.2°C, cooling slightly to around 17°C over the coming days
Waves: 1.9m
At 17.2 °C the water in São Martinho do Porto is fresh. Fine for a dip, but the first minute bites.
Sunrise: 07:44 · Sunset: 19:00 · Day length: 11h 16m
| Day | Sea water | Waves |
|---|---|---|
| Monday 12/10 | 17.2 °C | 1.9 m |
| Tuesday 13/10 | 16.9 °C | 1.8 m |
| Wednesday 14/10 | 17.0 °C | 1.8 m |
| Thursday 15/10 | 16.9 °C | 2.0 m |
| Friday 16/10 | 16.7 °C | 2.1 m |
| Saturday 17/10 | 16.8 °C | 2.4 m |
| Sunday 18/10 | 16.6 °C | 2.4 m |
| Month | Average water |
|---|---|
| January | 15.4 °C |
| February | 15.1 °C |
| March | 15.0 °C |
| April | 15.9 °C |
| May | 16.3 °C |
| June | 17.7 °C |
| July | 17.4 °C |
| August | 16.9 °C |
| September | 16.9 °C |
| October | 18.2 °C |
| November | 17.5 °C |
| December | 16.0 °C |
Monthly averages for 2022–2025.
This page shows the water temperature at São Martinho do Porto today and over the next seven days, so you can pick the best beach day before you go.
Sea temperature moves much more slowly than air temperature. A hot afternoon does not warm the ocean, and a windy day can cool it fast. Checking the water itself is the only reliable way to know what to expect.
São Martinho do Porto sits inside a shell-shaped bay that closes to a narrow opening, almost sealing it off from the open sea. That geometry keeps the swell out and lets the enclosed water warm and settle, so it runs flatter and a little milder than the exposed coast on either side, at about 16.7 °C in August. It is one of the calmest and safest beaches on the west coast, and the shallow inner curve is warmer again on a sunny afternoon.
The water is warmest in October, averaging 18.2 °C, and coldest in March at 15.0 °C. On the west coast the peak arrives late, in early autumn, because summer upwelling keeps pulling cold deep water to the surface.
The ocean gains and loses heat far more slowly than land, so it runs months behind the seasons. On top of that, the summer northerly wind pushes surface water offshore and draws cold deep water up in its place, which is why a heatwave on land so often coincides with a colder sea.
The enclosed bay gives some of the safest swimming on the west coast, with barely any swell and warm shallows around the inner curve. Kayaks, paddleboards and pedalos work the flat water, and the walk out along the cliff to the narrow bay mouth is short and rewarding. Families come back here year after year for exactly this reason.