São Luís
Brazil
Long-term weather forecast
Long-term weather forecast

December weather forecast and climate
São Luís, Brazil

The first month of the summer, December, is also a hot month in São Luís, Brazil, with average temperature fluctuating between 24°C (75.2°F) and 31.1°C (88°F).
The ideal sea water temperature of 28.1°C (82.6°F) and only 4 rainfall days, with 77.4mm (3") of accumulated rainfall, make December the best time for swimming and other water activities.

Temperature

In December, the average high-temperature in São Luís, Brazil, is relatively the same as in November - a still tropical 31.1°C (88°F). In December, the average low-temperature is 24°C (75.2°F).

Heat index

The average heat index in December is appraised at a very hot 38.2°C (100.8°F). Take extra precautions, as heat cramps and heat exhaustion are possible. Sustained activity may result in heatstroke.
Note that heat index values are valued for light wind and location in the shade. Exposure to direct sunshine can increase heat index values by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'real feel', 'feels like', 'apparent temperature', or 'felt air temperature', is an index that combines air temperature and relative humidity to determine the human-perceived temperature equivalent. This effect is individual, with diverse people perceiving weather differently for numerous reasons (pregnancy, wind, clothing), and activity. Bear in mind that direct sunshine exposure increases weather impact, and may raise heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are especially crucial for babies and toddlers. Young children are generally more endangered than adults, as they usually less sweat. And also, due to larger skin surface relative to their small bodies and higher heat production as a result of their activity.
The human body cools itself through perspiration, as excessive warmth is removed from the body through sweat evaporation. When the relative humidity is high, the evaporation rate is reduced. The warmth is removed from the body at a lower rate, causing the body to retain more heat than it would in dry air. When heat gain surpasses the level the body can shed, body temperature begins to increase, and consequently, overheating and dehydration can occur, with varying severity.

Humidity

December is the least humid month in São Luís, with an average relative humidity of 71%.

Rainfall

In São Luís, Brazil, during 4 rainfall days, 77.4mm (3") of precipitation is typically accumulated. In São Luís, during the entire year, the rain falls for 130 days and collects up to 2290.2mm (90.2") of precipitation.

Sea temperature

In São Luís, the average water temperature is 28.1°C (82.6°F).
Note: Water temperature between 25°C (77°F) and 29°C (84.2°F) is regarded as very warm and enjoyable by all. With these temperatures, water activities are pleasurable, without feeling uncomfortable for prolonged periods.

Daylight

Months with the longest days are January and December, with an average of 12.3h of daylight.

Sunshine

In December, the average sunshine in São Luís is 6.7h.

UV index

Months with the highest UV index are January through April, September through December, with an average maximum UV index of 12. A UV Index reading of 11, and higher, represents an excessive health risk from unprotected exposure to the Sun's UV rays for the ordinary person.
Note: In December, the average maximum UV index of 12 translate into the following recommendations:
Take all required precautions, as unprotected skin and eyes can burn in minutes. The Sun's UV radiation is most powerful between 10 a.m. and 4 p.m. To the extent possible, limit exposure to the direct sun during these hours. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun. Even on cloudy days, a sunscreen with a minimum 30 sun protection factor should be generously applied and frequently re-applied, including after every swim or outdoor exercise. Beware! The strength of the UV rays is significantly increased by the reflection of the water and sand.

What is the temperature in December in São Luís?

The average high-temperature, in December, is 31.1°C (88°F), while the average low-temperature is 24°C (75.2°F). The average heat index (a.k.a. 'real feel', 'feels like'), that combines air temperature and relative humidity, in December is calculated to 38.2°C (100.8°F).

What is the least humid month in São Luís?

With an average relative humidity of 71%, December is the least humid month in São Luís, Brazil.

What is the average humidity in December in São Luís?

The average relative humidity in December is 71%.

How many days does it rain in December in São Luís?

In December, in São Luís, Brazil, the rain falls for 4 days. Throughout December, 77.4mm (3") of precipitation is accumulated.

What is the sea water temperature in December in São Luís?

In December, the average sea temperature is 28.1°C (82.6°F). For any water activity, surface water temperatures between 25°C (77°F) and 29°C (84.2°F) are considered as excellent and extremely pleasant for lengthened periods.

When are the longest days in São Luís?

January and December, with an average of 12.3h of daylight, are months with the longest days in São Luís, Brazil.

How many hours of daylight does São Luís have in December?

In São Luís, Brazil, the average length of the day in December is 12.3h.

How many hours of sunshine does São Luís have in December?

In São Luís, the average sunshine in December is 6.7h.

What is the month with the highest UV index in São Luís?

Months with the highest UV index in São Luís, Brazil, are January through April, September through December, with an average maximum UV index of 12.

How high is the UV index in December in São Luís?

In December, the average daily maximum UV index is 12. A UV Index estimate of 11, and higher, represents an extreme health threat from the exposure to the Sun's UV radiation.
Average temperature in December - São Luís, Brazil
  • Average high temperature in December: 31.1°C

The warmest month (with the highest average high temperature) is November (31.4°C).
Months with the lowest average high temperature are February and March (29.4°C).

  • Average low temperature in December: 24°C

Months with the highest average low temperature are November and December (24°C).
The coldest month (with the lowest average low temperature) is July (22.6°C).

Average humidity in December - São Luís, Brazil
  • Average humidity in December: 71%

The month with the highest relative humidity is April (90%).
The month with the lowest relative humidity is December (71%).

Average rainfall in December - São Luís, Brazil
  • Average rainfall in December: 77.4mm

The wettest month (with the highest rainfall) is April (475.9mm).
The driest month (with the lowest rainfall) is October (7.6mm).

Average rainfall days in December - São Luís, Brazil
  • Average rainfall days in December: 4 days

The month with the highest number of rainy days is March (23 days).
Months with the lowest number of rainy days are October and November (1 days).

Average sea temperature in December - São Luís, Brazil
  • Average sea temperature in December: 28.1°C

The best month for swimming (with the highest average sea temperature) is March (28.9°C).
The coldest month (with the lowest average sea temperature) is September (27.3°C).

Average daylight in December / Average sunshine in December - São Luís, Brazil
  • Average daylight in December: 12.3h

Months with the longest days are January and December (Average daylight: 12.3h).
Months with shortest days are May, June, July and August (Average daylight: 12h).

  • Average sunshine in December: 6.7h

The month with most sunshine is August (Average sunshine: 8.4h).
The month with least sunshine is March (Average sunshine: 3.5h).

Average UV index in December - São Luís, Brazil
  • Average UV index in December: 12

Months with the highest UV index are January, February, March, April, September, October, November and December (UV index 12).
Months with the lowest UV index are June and July (UV index 10).