Weather in Porto Alegre in May

Prime time. If you get to pick your dates, May is the one. Highs average 21.6 °C, lows 12.4 °C, and rain falls on 11 days — nothing in the month is working against you.

May ranks 2 of 12 in Porto Alegre. Only April scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain on 11 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. 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. Across the twenty years measured, the hottest May day reached 30.8 °C and the coldest night fell to 1.5 °C, and the wettest single day dropped 68 mm — roughly 61% of the month's rain in one day.

May is moderately variable: 41 mm in the driest year against 222 mm in the wettest, around an average of 112 mm. Roughly two Mays in three land near that average, and the third does something else entirely.

Wind is light at 7.5 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 84%, high enough to notice on the warm days without dominating them.

How May sits in the year

The month is on the way down: 4.3 °C cooler than April, with June dropping another 2.2 °C. The first week and the last are not the same trip.

Daylight in May

May sits at the dark end of Porto Alegre's year — 10.6 hours of daylight against 14.1 at midsummer, losing 0.6 hours across the month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

Sea temperature

The sea sits at about 20.8 °C in May — swimmable, but it takes a moment to commit. The sea peaks at 25.3 °C in February and bottoms out at 16.5 °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

Peak season. Expect the highest prices of the year and to be booking well ahead. If the dates are flexible, September is the trade worth considering — 6 points weaker on weather, and materially quieter.

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

May in Porto Alegre versus nearby

If Porto Alegre is one option among several, the nearby comparison is worth making. Curitiba is close enough to be a coin toss — within a degree on temperature, 2 days more rain. São Paulo is close enough to be a coin toss — within a degree on temperature, 1 day less rain.

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

Every month in Porto Alegre

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