September weather forecast and climate
Colombo, Sri Lanka

Statues on the Seema Malaka Temple in Colombo, Sri Lanka, overlooking the Beira Lake
Statues on the Seema Malaka Temple in Colombo, Sri Lanka, overlooking the Beira Lake

Weather in September

September, the first month of the autumn, in Colombo, is also a moderately hot month, with average temperature fluctuating between 24.9°C (76.8°F) and 29.1°C (84.4°F).

Temperature

In September, the average high-temperature is essentially the same as in August - a still moderately hot 29.1°C (84.4°F). In Colombo, in September, the average low-temperature is 24.9°C (76.8°F).

Heat index

In September, the average heat index is calculated to be a very hot 35.2°C (95.4°F). Take special precautions - heat exhaustion and heat cramps are expected. Heatstroke may occur with lengthy activity.
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 'apparent temperature', 'felt air temperature', 'feels like', or 'real feel', is what the temperature feels like to the human body when the air temperature is combined with the relative humidity. This effect is subjective, depending on the activity and individual's heat perception influenced by various reasons (wind, clothing, differences in body mass, height, and shape). 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.
Perspiration is the human body's physiological response to high temperatures and is an attempt to lower body temperature through evaporation of sweat. High relative humidity reduces the evaporation rate, resulting in a lower heat removal rate from the body, causing the perception of being overheated. If the body can not disperse the excessive heat and body temperature reaches conditions of hyperthermia, above 37.5°C (99.5°F) to 38.3°C (100.9°F), thermal conditions are potentially life-threatening.

Humidity

In September, the average relative humidity is 81%.

Rainfall

In Colombo, Sri Lanka, in September, during 26.9 rainfall days, 206mm (8.11") of precipitation is typically accumulated. In Colombo, Sri Lanka, during the entire year, the rain falls for 289.4 days and collects up to 2262mm (89.06") of precipitation.

Sea temperature

In Colombo, the average seawater temperature is 27.8°C (82°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

In Colombo, the average length of the day is 12.2h.

Sunshine

The average sunshine in September is 7.4h.

UV index

January through April, July, September, November and December, with an average maximum UV index of 7, are months with the highest UV index in Colombo. A UV Index reading of 6 to 7 represents a high health vulnerability from the exposure to the Sun's UV radiation for the ordinary person.
Note: The daily maximum UV index of 7 interpret into the following advice:
Take precautions and utilize sun safety practices. Protection against the skin and eye damage is required. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. 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. Beware! The strength of the UV rays is significantly increased by the reflection of the water and sand.
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FAQ

What is the temperature in September in Colombo?

The average high-temperature, in September, is 29.1°C (84.4°F), while the average low-temperature is 24.9°C (76.8°F). In September, the average heat index (a.k.a. 'felt air temperature', 'real feel'), which calculates the temperature value influenced by the moisture in the air, is calculated to be 35.2°C (95.4°F).

What is the average humidity in September in Colombo?

In Colombo, Sri Lanka, the average relative humidity in September is 81%.

How many days does it rain in September in Colombo?

In September, the rain falls for 26.9 days. Throughout September, 206mm (8.11") of precipitation is accumulated.

How warm is the water in September in Colombo?

In Colombo, Sri Lanka, in September, the average water temperature is 27.8°C (82°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.

How many hours of daylight does Colombo have in September?

In Colombo, Sri Lanka, the average length of the day in September is 12.2h.

How long on average sun shines in September in Colombo?

In Colombo, Sri Lanka, the average sunshine in September is 7.4h.

What is the month with the highest UV index in Colombo?

January through April, July, September, November and December, with an average maximum UV index of 7, are months with the highest UV index in Colombo.

What is the UV index intensity in September in Colombo?

The average daily maximum UV index in September is 7. A UV Index of 6 to 7 symbolizes a high health vulnerability from the exposure to the Sun's UV radiation.

Average temperature in September
Colombo, Sri Lanka

Average temperature in September - Colombo, Sri Lanka
  • Average high temperature in September: 29.1°C

The warmest months (with the highest average high temperature) are March and April (31.8°C).
Months with the lowest average high temperature are July and August (28.9°C).

  • Average low temperature in September: 24.9°C

The month with the highest average low temperature is May (26.3°C).
The coldest month (with the lowest average low temperature) is January (23.1°C).

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Average pressure in September
Colombo, Sri Lanka

Average pressure in September - Colombo, Sri Lanka
  • Average pressure in September: 1009.8mbar

The month with the highest atmospheric pressure is January (1011.6mbar).
The month with the lowest atmospheric pressure is May (1008.6mbar).

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Average wind speed in September
Colombo, Sri Lanka

Average wind speed in September - Colombo, Sri Lanka
  • Average wind speed in September: 13.2km/h

The windiest month (with the highest average wind speed) is June (15.1km/h).
The calmest month (with the lowest average wind speed) is March (8km/h).

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Average humidity in September
Colombo, Sri Lanka

Average humidity in September - Colombo, Sri Lanka
  • Average humidity in September: 81%

Months with the highest relative humidity are June, July and August (83%).
Months with the lowest relative humidity are January and February (74%).

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Average rainfall in September
Colombo, Sri Lanka

Average rainfall in September - Colombo, Sri Lanka
  • Average rainfall in September: 206mm

The wettest month (with the highest rainfall) is June (341mm).
The driest month (with the least rainfall) is January (40mm).

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Average rainfall days in September
Colombo, Sri Lanka

Average rainfall days in September - Colombo, Sri Lanka
  • Average rainfall days in September: 26.9 days

The month with the highest number of rainy days is August (30.2 days).
The month with the least rainy days is January (11.6 days).

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Average sea temperature in September
Colombo, Sri Lanka

Average sea temperature in September - Colombo, Sri Lanka
  • Average sea temperature in September: 27.8°C

The best month for swimming (with the highest average sea temperature) is April (29.6°C).
The coldest month (with the lowest average sea temperature) is August (27.2°C).

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Average daylight in September /
Average sunshine in September
Colombo, Sri Lanka

Average daylight in September / Average sunshine in September - Colombo, Sri Lanka
  • Average daylight in September: 12.2h

Months with the longest days are June and July (Average daylight: 12.5h).
The month with the shortest days is December (Average daylight: 11.7h).

  • Average sunshine in September: 7.4h

The month with the most sunshine is January (Average sunshine: 9.1h).
The month with the least sunshine is November (Average sunshine: 6.7h).

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Average sunshine days in September
Colombo, Sri Lanka

Average sunshine days in September - Colombo, Sri Lanka
  • Average sunshine days in September: 1.5 days

The month with the most sunshine days is January (17.2 days).
Months with the least sunshine days are June and August (0.3 days).

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Average UV index in September
Colombo, Sri Lanka

Average UV index in September - Colombo, Sri Lanka
  • Average UV index in September: 7

Months with the highest UV index are January, February, March, April, July, September, November and December (UV index 7).
Months with the lowest UV index are May, June, August and October (UV index 6).

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Average cloud cover in September
Colombo, Sri Lanka

Average cloud cover in September - Colombo, Sri Lanka
  • Average cloud cover in September: 55

The month with the most cloud cover is June (Cloud cover 57).
The month with the least cloud cover is January (Cloud cover 24).

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Average visibility in September
Colombo, Sri Lanka

Average visibility in September - Colombo, Sri Lanka
  • Average visibility in September: 9km

Months with the highest visibility are January, February, March, April and December (10km).
Months with the lowest visibility are May, June, July, August, September, October and November (9km).

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