Climate and monthly weather forecastSão Luís, Brazil

The climate of São Luís

Perched on the northeastern coast of Brazil, São Luís dwells under the rule of the Aw or Tropical savanna climate as per the Köppen climate classification. Throughout the year, temperature rates in São Luís remain consistently high, oscillating slightly between a low-point of 22.6°C (72.7°F) and peaking at 31.4°C (88.5°F). This pleasant warmth couples with unwavering humidity levels, which sway slightly from 71% to 90%, creating an atmosphere that feels perpetually sultry.

Much like the heat and the humidity, patterns of rainfall and cloudiness also paint a vivid image of São Luís's climate. From a meteorological viewpoint, the rainfall figures present an interesting dynamic. Precipitation ranges from a marginal 8mm (0.31") in November to a downpour of 476mm (18.74") in April, with the number of rainy days per month following a similar pattern. Simultaneously, the duration of daily sunshine and daylight hours ebbs and flows minimally throughout the year. Daylight hovers around the 12-hour mark throughout the entirety of the year with sunshine durations fluctuating between 3.5 hours and 8.4 hours per day. Coupled with a UV index that never falls below 10, the climate offers a constant reminder of the city's position near the equator.

The sea temperature shadows the trends of the ambient climate, maintaining a relatively steady heat between 27.3°C (81.1°F) and 28.9°C (84°F) over the year. Together, these patterns of heat, rainfall and humidity create a landscape that is undeniably tropical, typifying the concept of a tropical savanna climate.

The best time to visit São Luís

In consideration of weather conditions, the period from mid-August to mid-November emerges as the prime time to visit São Luís. With rainfall levels dwindling between 8mm (0.31") and 29mm (1.14") and the number of rainy days not exceeding four, the city enjoys its driest phase. Concurrently, the average lowest temperature hovers around 23°C (73.4°F) while the high hits around 31°C (87.8°F), thus providing warmth without overpowering heat. For sunseekers, this period boasts of ample sunshine, with daylight spanning an average of 12 hours and average daily sunshine lasting over eight hours.

The worst time to visit São Luís

By contrast, the peak of São Luís's rainy season from February to May might constitute the least favorable time to traverse the city. Rainfall during this period rises to extreme levels, reaching a peak of 476mm (18.74") in April. Besides, the frequency of rainy days in these months exceeds 17 days each, possibly hindering outdoor activity plans. Higher humidity levels, touching 90%, and reduced sunshine hours also characterize this period, further reinforcing its status as the least desirable time for visitation.

Spring weather in São Luís

In São Luís, spring unfurls in a multiplicity of colors and welcomes the change of seasons. While September and October savor minimal rainfall, November experiences a slight increase to 11mm (0.43"). The temperature during spring fluctuates in a narrow band, with the lowest average temperature being 23.5°C (74.3°F) in September and the highest around 31.4°C (88.5°F) in November. Sunshine hours decrease marginally over these months, but with an average of over eight hours of sunlight daily and ample warmth, spring in São Luís can be quite pleasant.

Summer weather in São Luís

The summer months in São Luís, from December to February, introduce the city's wet season. With rainfall levels escalating from 77mm (3.03") in December to 373mm (14.69") in February, the city experiences a transition towards heavier precipitation. Temperature averages during this period swing from 24°C (75.2°F) to 30°C (86°F), ensuring warm and humid conditions thanks to the significant rain. Despite the increased downpour, daylight hours remain consistent around 12 hours per day, with sunshine hours dropping to their yearly minimum in February.

Autumn weather in São Luís

Autumn in São Luís marks the height of the rainy season. Precipitation in this period surges to its yearly peak, culminating at 476mm (18.74") in April and tapering off to 173mm (6.81") by June. Correspondingly, the number of rainy days each month also reaches a high between March and May. Despite the increased rainfall, temperatures continue to maintain a steady warmth, averaging between 22.9°C (73.2°F) and 30.4°C (86.7°F) over these months. However, with reduced daily sunshine hours, the overall weather can feel cloudy, damp, and humid.

Winter weather in São Luís

Winter months in São Luís, from July to August, draw the curtain on the heavy rains as the precipitation diminishes to 29mm (1.14") in August. The reduction in rainfall coincides with a marginal dip in temperature, with average lows settling around 22.6°C (72.7°F) and highs peaking near 30.7°C (87.3°F). Corresponding to the decrease in rain, the number of rainy days falls remarkably, and sunshine hours increase once again, bringing back the sun-soaked, tropical atmosphere of the city.

Weather in January

January is firmly within São Luís's rainy season, bringing high humidity and frequent rainfall. The month witnesses a temperature range from 23.5°C (74.3°F) as the nightly low to a daily high of 30°C (86°F). Daylight, meanwhile, extends up to 12.3 hours. Weather in January »

Weather in February

In February, weather in São Luís fluctuates minimally from January’s patterns, experiencing still high, but slightly less intense temperatures. Rainfall volume increases remarkably from January's 244mm (9.61") to a heavier 373mm (14.69"). Weather in February »

Weather in March

The month of March brings the most precipitation to São Luís, with 428mm (16.85") of rain spread across 23 days, the highest throughout the year. As temperatures inch from 23°C (73.4°F) at night to 29.4°C (84.9°F) in the day, humidity also scales upward. Weather in March »

Weather in April

April carries on the pattern of high rainfall in São Luís, with the volume peaking at 476mm (18.74"). Despite significant levels of precipitation, temperatures slightly rise, leading the mercury from 23.1°C (73.6°F) to 29.6°C (85.3°F). Weather in April »

Weather in May

May presages a shift in São Luís's weather, with a relative decrease in rainfall to 317mm (12.48"), signaling the approaching end of the wet season. Temperatures consistently loiter in the warm range. The solstice is a month away, bringing about subtle reduction in daylight hours to 12 hours from past months. Weather in May »

Weather in June

São Luís experiences a significant dip in rainfall in June, moving further away from the wet season. This reduction in rainfall, to 173mm (6.81"), is coupled with marginally cooler average sea temperatures. Daylight continues to clock at 12 hours for the sixth consecutive month. Weather in June »

Weather in July

July marks a notable change in São Luís's weather patterns, with rainfall dipping significantly to 131mm (5.16"), highlighting the progression of the dry season. The temperature scale reveals a slight dip in comparison to June. Moreover, daylight hours maintain their consistency, registering yet again at 12 hours. Weather in July »

Weather in August

August asserts itself as the driest month of the year in São Luís, with a mere 29mm (1.14") of rainfall. The gradual shift towards cooler temperatures, which began in July, continues into August. The month's 12 hours of daylight are complemented by a UV index of 11. Weather in August »

Weather in September

With mere 23mm (0.91") of rain, September mirrors August's patterns closely and continues to assert São Luís's dry season. There are marginal fluctuations in temperature compared to August, highlighting the ongoing cooler phase. Weather in September »

Weather in October

In October, São Luís experiences slightly increased rainfall to 8mm (0.31"), indicating a trend towards the upcoming wet season. Temperatures persist in a stable range, reflecting a mild climate. Daylight hours subtly increase to 12.2 along with a sustained UV index at 12, similar to September. Weather in October »

Weather in November

November witnesses a slight increase in rainfall reaching 11mm (0.43"), signaling the slow approach of the heavy rainfall typical of São Luís’s wet season. Meanwhile, temperatures remain relatively stable. With minor variations, daylight hours continue to extend up to 12.2, ensuring adequate sun hours. Weather in November »

Weather in December

The climatic conditions in December represent an upswing towards São Luís's rainy season with an increase in rainfall levels to 77mm (3.03"). As temperatures maintain a familiar range, daylight hours remain consistent with preceding months at 12.3 hours. Weather in December »