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Sao Luis has a hot, humid equatorial climate (Koppen Aw) with two clear seasons: a heavy rainy season from January to July and a dry season from August to December. Temperatures barely move, sitting between 23 and 34 degrees Celsius all year, but rainfall swings from around 450 mm in March and April to under 10 mm in September and October. This best time to visit guide explains how those two seasons shape a trip, and the things to do list covers what to see once you are here.
Sao Luis Weather by Month: Temperatures and Rainfall
The table below shows long-term monthly averages recorded at Marechal Cunha Machado airport, 13 km from the historic centre. Highs stay between 30 and 34 degrees Celsius and lows between 23 and 25 degrees Celsius every single month. For an overview of the whole city, start with the Sao Luis city guide.
| Month | Avg high (C) | Avg low (C) | Rainfall (mm) |
|---|---|---|---|
| January | 31.1 | 24.2 | 235 |
| February | 30.6 | 24.0 | 308 |
| March | 30.3 | 23.8 | 453 |
| April | 30.6 | 23.8 | 431 |
| May | 31.3 | 23.9 | 312 |
| June | 31.5 | 23.5 | 174 |
| July | 31.5 | 23.4 | 111 |
| August | 32.0 | 24.7 | 23 |
| September | 32.3 | 24.4 | 3 |
| October | 32.5 | 24.7 | 3 |
| November | 33.5 | 24.9 | 10 |
| December | 32.2 | 25.0 | 55 |
Sao Luis Weather by Month: January to April
January to April is the wettest stretch of the year. March is the single wettest month with 453 mm of rain, followed by April at 431 mm, and February is not far behind at 308 mm. Rain tends to fall in heavy afternoon and evening downpours rather than all-day drizzle, so mornings are often still usable. Highs run 30 to 31 degrees Celsius and humidity sits near 85 percent, which makes the heat feel heavier. If you visit in these months, pack a light rain jacket and plan indoor sightseeing like the historic centre museums, and check the where to stay guide for hotels with good air conditioning.
Sao Luis Weather by Month: May to August
Rain eases steadily from May (312 mm) through June (174 mm) to July (111 mm), and by August it has dropped to just 23 mm. This is the transition into the dry season and one of the better stretches to be outdoors. Highs climb slightly to 31 to 32 degrees Celsius in July and August while lows sit near 23 to 25 degrees Celsius. August is a strong month for beach days on Calhau and Sao Marcos and for a ferry trip to Alcantara.
Sao Luis Weather by Month: September to December
September and October are the driest months, each averaging only about 3 mm of rain, and November is also dry at 10 mm. These are the hottest months of the year: November peaks at an average high of 33.5 degrees Celsius. Sunshine is at its most reliable from September to December, and this is when the lagoons of nearby Lencois Maranhenses are at their fullest, though the dunes themselves start to dry out by late October. December brings the first real rain back, around 55 mm, as the wet season begins to return. Before you go, the neighborhoods guide maps the districts, and the travel tips guide covers airport transfers.
Sao Luis Weather by Month: Humidity, Sunshine and Sea Temperature
Relative humidity runs between 77 and 85 percent all year, with the highest readings in the rainy season. The city records roughly 2,400 hours of sunshine a year, with the sunniest period from August to December. Sea temperatures off the coast stay between 27 and 28 degrees Celsius year-round, so swimming is comfortable in any month. For month-by-month events, see the events and festivals guide.
