Weather in Porto in August

How August compares

August is the 1st warmest month of the year in Porto and ranks 119th of 134 destinations we compare for August - see where else is hot in August. Within Portugal it is 11th of 13 (Portugal in August). Against London's average high of 21.4°C in August, Porto is 4.5°C warmer by day and 3.6°C warmer at night.

Daytime and night-time in August

The typical August day in Porto peaks at 25.9°C, but that is an average: the warmest 10% of days reach 31.5°C or more. About 50% of days top 25°C and 1 in 6 pass 30°C. Nights average 17.1°C; one night in ten drops to 14.6°C or lower, so pack a layer for evenings. Between 1991 and 2020 the hottest August day here reached 37.6°C (2003-08-07) and the coldest night 12.4°C (1991-08-23).

Rain in August

Some rain (4-8 rainy days): about 5 days with 1 mm or more, 30 mm in total. Year to year it varies a lot - the wettest August was 2004 with 125 mm, the driest 2018 with 1 mm. Humidity averages 73%.

Sea temperature in August

The sea averages 17.4°C - too cold for most (under 18°c). Depending on the year it ranges from 16.5°C to 18.4°C. For the warmest sea here, come in September (17.5°C).

Sunshine and daylight

Around 8.9 hours of sunshine a day (estimated from cloud cover), 13.6 hours of daylight: the sun rises about 06:44 and sets about 20:34 local time in mid-August. Average cloud cover is 35%.

Is August a good time to visit Porto?

Yes - it is one of the better months: hot days, manageable rain and long sunny days. The best months for Porto on our scoring are July, August, September; months averaging 25°C or more: Jul, Aug.

Warm days, with occasional stronger heat

Porto's August warmth suits travellers who want summer weather but do not need intense heat every day. Half of days reach 25°C, while 16% reach 30°C, so hot afternoons are a possibility rather than the daily rule. The warmest 10% of days reach 31.5°C or more: keep your plans flexible enough to take a shaded break around midday when temperatures climb. Light clothing makes sense during the day, but pack a jumper or light jacket for evenings. Average night lows are 17.1°C, and the coldest 10% of nights fall to 14.6°C or below, which can feel cool after a warm afternoon.

Plenty of sunshine, but leave room for rain

August gives you plenty of scope for outdoor plans, with about 8.9 hours of sunshine within 13.6 hours of daylight. That does not mean an uninterrupted run of clear skies, so avoid making every day depend on sunshine. There are about 4 rainy days during the month: rain is a possible interruption, not a reason on its own to rule August out. A light waterproof is a sensible addition to your bag, alongside sunglasses and sun protection. Keep some flexibility to move outdoor time to a drier spell rather than assuming you will need to spend a wet day entirely indoors.

The sea is the main catch

Do not confuse warm city weather with warm swimming conditions. The sea averages 17.4°C in August, with a year-to-year range of 16°C to 18°C, so it remains cold even during Porto's warmest month. If you enjoy a brief, bracing dip, that may be acceptable; if you want to stay in the water comfortably for a long time, it is a clear drawback. Treat swimming as an optional part of the trip rather than its main purpose. Pack something dry and warm to put on afterwards, especially if you plan to stay outdoors into the evening as the air temperature drops.