Weather in Lisbon in May

Prime time. May is about as good as Lisbon gets. Highs average 19 °C, lows 14.5 °C, and rain falls on 6 days — nothing in the month is working against you.

May ranks 5 of 12 in Lisbon: past the worst of the year but short of July, which is the month to book if the dates are open.

Rain falls on only 6 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 May reaches 30 °C; the day barely swings — 4.5 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest May day reached 27.8 °C and the coldest night fell to 10.6 °C, and the wettest single day dropped 26 mm — roughly 84% of the month's rain in one day.

May is moderately variable: 1 mm in the driest year against 97 mm in the wettest, around an average of 31 mm. Roughly two Mays in three land near that average, and the third does something else entirely.

Wind sits around 16.6 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 79%, high enough to notice on the warm days without dominating them.

How May sits in the year

The month is on the way up: 2.1 °C warmer than April, and June adds another 2 °C. Late in the month feels noticeably different from the start of it, which is worth knowing if the trip is short.

Daylight in May

May is at or near the longest days of Lisbon's year: 14.3 hours of daylight, gaining 0.9 hours across the month. Evenings are the real gain — dinner outdoors still happens in full light.

Sea temperature

The sea sits at about 17.1 °C in May — cold — a quick dip rather than a swim, and a wetsuit if you are in for longer. The sea peaks at 20.7 °C in September and bottoms out at 15.3 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

How busy it gets

Shoulder. The value months — prices ease off and you get the place closer to itself. May is the value pick for Lisbon: it scores within 12 points of July without carrying July's prices.

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

May in Lisbon versus nearby

If Lisbon is one option among several, the nearby comparison is worth making. Évora is close enough to be a coin toss — 6.3 °C warmer, the same number of rain days. Leiria is close enough to be a coin toss — 5 °C warmer, 2 days more rain.

So: May works, with July the better month by 12 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Lisbon

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