Rio de Janeiro
Brazil
Long-term weather forecast
Long-term weather forecast

December weather forecast and climate
Rio de Janeiro, Brazil

The first month of the summer, December, is also a moderately hot month in Rio de Janeiro, Brazil, with temperature in the range of an average high of 28.2°C (82.8°F) and an average low of 23°C (73.4°F).

Temperature

In December, the average high-temperature is relatively the same as in November - a still warm 28.2°C (82.8°F). The average low-temperature, in December, is 23°C (73.4°F).

Heat index

In December, the average heat index is estimated at a hot 32.8°C (91°F). Take extra precautions, as heat cramps and heat exhaustion are possible. Sustained activity may result in heatstroke.
Take into consideration that the heat index values are calculated for shade and light wind conditions. Exposure to direct sunshine can increase heat index values by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like', 'felt air temperature', 'apparent temperature', or 'real feel', is calculated by taking the relative humidity value for a specific location and factoring it into the air temperature reading. Additional factors like activity, metabolic differences, differences in body mass, height, and shape, and wind affect individual temperature impact. 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 particularly important for children. 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.

Humidity

In Rio de Janeiro, the average relative humidity in December is 81%.

Rainfall

In December, in Rio de Janeiro, Brazil, the rain falls for 21.9 days. Throughout December, 98mm (3.86") of precipitation is accumulated. Throughout the year, in Rio de Janeiro, there are 192.5 rainfall days, and 812mm (31.97") of precipitation is accumulated.

Sea temperature

In Rio de Janeiro, Brazil, in December, the average water temperature is 24°C (75.2°F).
Note: A person's cold intolerance, with sunshine, wind, and air temperature, are essential factors for enjoying swimming in 24°C (75.2°F) water. (FYI: The Olympic swimming competition requires a water temperature between 25°C (77°F) and 28°C (82.4°F).)

Daylight

With an average of 13.5h of daylight, December has the longest days of the year.

Sunshine

In Rio de Janeiro, the average sunshine in December is 8.3h.

UV index

In Rio de Janeiro, the average daily maximum UV index in December is 6. A UV Index of 6 to 7 symbolizes a high health risk from unprotected exposure to the Sun's UV rays for average individuals.
Note: In December, the average maximum UV index of 6 translate into the following recommendations:
Take precautions against overexposure. Fair-skinned people may get burned in less than 20 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. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects. Caution! The reflection of sand and water significantly increases the intensity of the Sun's UV radiation.

What is the temperature in December in Rio de Janeiro?

The average high-temperature, in December, in Rio de Janeiro, is 28.2°C (82.8°F), while the average low-temperature is 23°C (73.4°F). In December, the average heat index (a.k.a. 'feels like', 'apparent temperature'), that combines relative humidity and air temperature, is calculated to 32.8°C (91°F).

What is the average humidity in December in Rio de Janeiro?

In Rio de Janeiro, the average relative humidity in December is 81%.

How much does it rain in Rio de Janeiro in December?

In December, in Rio de Janeiro, Brazil, the rain falls for 21.9 days. Throughout December, 98mm (3.86") of precipitation is accumulated.

What is the sea temperature in December in Rio de Janeiro?

In Rio de Janeiro, Brazil, the average seawater temperature in December is 24°C (75.2°F). For individuals prone to feeling cold, swimming in 23°C (73.4°F) is still regarded as intolerable. A wetsuit is not a necessity, but sunshine, wind, and air temperature are essential factors for relishing swimming at 24°C (75.2°F).

When are the longest days in Rio de Janeiro?

The month with the longest days in Rio de Janeiro is December, with an average of 13.5h of daylight.

What is the average length of the day in December in Rio de Janeiro?

The average length of the day in December in Rio de Janeiro is 13.5h.

How many hours of sunshine does Rio de Janeiro have in December?

The average sunshine in December in Rio de Janeiro, Brazil, is 8.3h.

What is the UV index reading in December in Rio de Janeiro?

The average daily maximum UV index in December in Rio de Janeiro is 6. A UV Index of 6 to 7 symbolizes a high hazard to health from unsafe exposure to the Sun's UV rays.
Average temperature in December - Rio de Janeiro, Brazil
  • Average high temperature in December: 28.2°C

The warmest month (with the highest average high temperature) is February (29.7°C).
The month with the lowest average high temperature is July (24°C).

  • Average low temperature in December: 23°C

The month with the highest average low temperature is January (23.7°C).
The coldest month (with the lowest average low temperature) is August (18.5°C).

Average humidity in December - Rio de Janeiro, Brazil
  • Average humidity in December: 81%

The month with the highest relative humidity is November (82%).
The month with the lowest relative humidity is August (76%).

Average rainfall in December - Rio de Janeiro, Brazil
  • Average rainfall in December: 98mm

The wettest month (with the highest rainfall) is November (119mm).
The driest month (with the least rainfall) is June (29mm).

Average rainfall days in December - Rio de Janeiro, Brazil
  • Average rainfall days in December: 21.9 days

The month with the highest number of rainy days is March (22.7 days).
The month with the least rainy days is July (9.3 days).

Average sea temperature in December - Rio de Janeiro, Brazil
  • Average sea temperature in December: 24°C

The best month for swimming (with the highest average sea temperature) is March (25.8°C).
The coldest month (with the lowest average sea temperature) is September (21.6°C).

Average daylight in December / Average sunshine in December - Rio de Janeiro, Brazil
  • Average daylight in December: 13.5h

The month with the longest days is December (Average daylight: 13.5h).
The month with the shortest days is June (Average daylight: 10.7h).

  • Average sunshine in December: 8.3h

The month with the most sunshine is February (Average sunshine: 8.8h).
The month with the least sunshine is October (Average sunshine: 7.5h).

Average UV index in December - Rio de Janeiro, Brazil
  • Average UV index in December: 6

The month with the highest UV index is January (UV index 7).
The month with the lowest UV index is September (UV index 5).