September weather forecast
Colombo, Sri Lanka

The transition to a drier season begins in September, as rainfall decreases significantly to 206mm (8.11"). The decrease in cloud cover allows for increased visibility, making it a suitable month for sightseeing. The daylight hours, although gradually decreasing, remain adequate for daytime activities. A moderate upswing in wind speed might please sailing or kite-flying enthusiasts. Although the relief from the relentless rain brings welcomed dry spells, the temperatures persist in hovering in the mid to high 20s°C.

Temperature

Colombo notes an average high-temperature of a still warm 29.1°C (84.4°F) in September, displaying minor variation from August. The September average low temperature in Colombo, marginally lower than the daytime high, records at a still moderately hot 24.9°C (76.8°F).

Heat index

The average heat index in September is computed to be a torrid 35°C (95°F). Special measures are necessary to avoid heat cramps and heat exhaustion. Persistent activity could result in heatstroke.
The heat index's values are generally associated with conditions in shade and light breezes. The heat index could experience an increase of 15 Fahrenheit (8 Celsius) degrees due to direct sunlight.
Note: The heat index, also known as 'real feel' or 'feels like', quantifies the warmth felt when relative humidity is considered. Metabolic differences, pregnancy status, and the level of physical activity are additional factors influencing an individual's weather perception. In the direct sunlight, the weather's impact can be amplified, possibly boosting the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly relevant to children. Youngsters are usually more at risk than adults, considering they sweat less. Additionally, their high skin surface area compared to their little bodies and their high heat production due to activity increases their risk.
The natural cooling mechanism in humans involves perspiration, where the evaporation of sweat balances out excessive warmth. With a lot of moisture in the air, the evaporation process is not as effective, and the body does not cool down as efficiently, creating a perception of overheating. Heat-related challenges, like dehydration, can be anticipated when body heat isn't managed effectively.

Humidity

The average relative humidity in September in Colombo is 81%.

Rainfall

In Colombo, in September, during 26.9 rainfall days, 206mm (8.11") of precipitation is typically accumulated. Throughout the year, there are 289.4 rainfall days, and 2262mm (89.06") of precipitation is accumulated.

Sea temperature

In September, the average sea temperature in Colombo is 27.8°C (82°F).
Note: For activities in the water such as swimming or diving, temperatures from 25°C (77°F) to 29°C (84.2°F) are considered optimal for prolonged enjoyment without discomfort.

Daylight

The average length of the day in September is 12h and 10min.
On the first day of the month, sunrise is at 06:03 and sunset at 18:17. On the last day of September, in Colombo, sunrise is at 05:58 and sunset at 18:02 +0530.

Sunshine

In Colombo, Sri Lanka, 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. A UV Index value of 6 to 7 symbolizes a high health risk from unprotected exposure to Sun's UV rays for the ordinary person.
Note: A daily maximum UV index of 7 in September translates into the following instructions:
Follow precautions and abide by sun safety rules. Deterrence of sunburn is imperative. 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. Sunglasses that guard against UVA and UVB rays are pivotal in minimizing sun-induced ocular damage. Stay vigilant! UV rays get a boost in intensity due to sand and water reflections.