Weather in Lisbon in August

Prime time. If you get to pick your dates, August is the one. Highs average 23 °C, lows 17.9 °C, and rain falls on 1 days — nothing in the month is working against you.

August ranks 2 of 12 in Lisbon. Only July scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain falls on only 1 days, so an itinerary with no wet-weather fallback is a reasonable risk. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: it never really gets hot: not one day in an average August reaches 30 °C; the day barely swings — 5 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest August day reached 32.8 °C and the coldest night fell to 14.8 °C.

August is dependably dry, and that reliability is the point: across the twenty years measured, the wettest August on record still only managed 24 mm, and the driest managed 0 mm. There is no meaningful variability to plan around, which makes this one of the few months anywhere that you can build a fixed outdoor itinerary against without a fallback. The wettest single day in twenty years of Augusts brought 10 mm. Rain simply is not the variable that decides this trip — heat, crowds and cost are.

Wind sits around 16.2 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 81%, high enough to notice on the warm days without dominating them.

How August sits in the year

Temperatures hold steady either side: 22.2 °C in July, 23 here, 22.3 in September. Nothing about the timing within the month matters much.

Daylight in August

13.7 hours of daylight, losing 1.1 hours across the month. That is between Lisbon's extremes of 14.9 and 9.5 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 20.5 °C in August — swimmable, but it takes a moment to commit. This is the warmest the water gets all year.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead. If the dates are flexible, May is the trade worth considering — 12 points weaker on weather, and materially quieter.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

August in Lisbon versus nearby

If Lisbon is one option among several, the nearby comparison is worth making. Évora is the weaker option in August — 11.3 °C warmer, the same number of rain days. Leiria is the weaker option in August — 7.2 °C warmer, 1 day more rain.

So: August is effectively as good as it gets here — 0 points behind July, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Lisbon

See all twelve months in Lisbon, or where else to go in August.