September weather forecast
Dehiwala, Sri Lanka

As September arrives in Dehiwala, a distinct decrease in daily rainfall and cooler evenings commence. The weather pattern from August carries through with minor modulations, most notably in the declined precipitation. Setting a point of interest, September records 195mm (7.68") of rainfall, an appreciable decrease from the preceding month. As September nears its closure, residents anticipate the slight surge in temperature, setting the stage for the warmth in the upcoming October.

Temperature

The start of September marks an average high-temperature of a still moderately hot 29°C (84.2°F), hardly distinguishable from the conditions in August. During the nights of September, Dehiwala records an average temperature of 25.3°C (77.5°F), a minor drop from daytime peaks.

Heat index

The heat index value for September is estimated at a fiery hot 35°C (95°F). More protective measures are required - heat exhaustion and heat cramps are likely. Heatstroke may follow lengthy activity.
Take into consideration that the heat index values are calculated for shade and light wind conditions. If exposed to direct sunlight, the heat index could climb by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'real feel', shows a temperature sensation when both heat and moisture conditions are combined. The influence of weather can be personal, changing with an individual's body mass, height, and level of physical exertion. Exposure to direct sun rays can influence the heat you feel, pushing the heat index up by 15 Fahrenheit (8 Celsius) degrees. Heat index values are primarily vital for children. Children often overlook the need for breaks and fluid intake. Thirst is a late-stage sign of dehydration - hence, it is necessary to stay hydrated, especially during extended periods of physical activities.
The physiological way the human body responds to excessive heat is by inducing perspiration, using sweat evaporation as a cooling mechanism. When there is an excess of moisture in the atmosphere, the efficiency of the evaporation process is lessened, leading to less efficient body cooling and a sensation of overheating. Heat absorption that surpasses the body's shedding capability can lead to overheating and varying levels of dehydration.

Humidity

In Dehiwala, the average relative humidity in September is 82%.

Rainfall

In Dehiwala, during September, the rain falls for 25.4 days and regularly aggregates up to 195mm (7.68") of precipitation. In Dehiwala, during the entire year, the rain falls for 285.6 days and collects up to 2201mm (86.65") of precipitation.

Sea temperature

In September, the average sea temperature is 27.8°C (82°F).
Note: Swimming, diving, and other water endeavors at temperatures between 25°C (77°F) and 29°C (84.2°F) are considered enjoyable and satisfying for extended periods without discomfort.

Daylight

The average length of the day in September in Dehiwala 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, sunrise is at 05:58 and sunset at 18:02 +0530.

Sunshine

In September, the average sunshine in Dehiwala is 7.6h.

UV index

January through April, June, July, September, November and December, with an average maximum UV index of 7, are months with the highest UV index. A UV Index of 6 to 7 symbolizes a high threat to health from unprotected exposure to Sun's UV rays for average individuals.
Note: A maximum high UV index of 7 in September translates into the following recommendations:
Skirt overexposure. People with light complexions might get scorched in under 20 minutes. Between 10 a.m. and 4 p.m., UV radiation is strongest. Make an effort to avoid direct sunlight during this time, remembering that shade structures may not provide full sun protection. Wearing a wide-brim hat can block approximately 50% of UV radiation, protecting the eyes. Heads up! UV intensity is amplified by reflections from water and sand.