September weather forecast
Polonnaruwa, Sri Lanka

The onset of September brings about significant changes in the weather of Polonnaruwa. Increased rainfall, paired with stable temperatures, represents the transition into the rainy season. Significantly, the transition from a comparably dry August with 29mm (1.14") of rain to a wetter September with an average rainfall of 53mm (2.09") indicates the official start of the rainy season.

Temperature

The average high-temperature during September is a still hot 33.9°C (93°F), almost matching the conditions of the preceding month. Polonnaruwa sees an average low-temperature of 24.1°C (75.4°F) during September.

Heat index

The average heat index in September is computed to be a blazing hot 45°C (113°F). Be alert: Heat exhaustion along with heat cramps are probable. Heatstroke is a threat with sustained physical activity.
The heat index's values are generally associated with conditions in shade and light breezes. The direct sun can potentially cause the heat index to increase by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'apparent temperature', reflects the feeling of heat when considering both air temperature and humidity. The impact of weather on an individual can be subjective, affected by the person's activity and heat perception, which can vary due to elements including wind, clothing, and metabolic differences. It is noteworthy to mention that direct sunlight exposure can augment the felt temperature, leading to an increase in the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly meaningful for babies and toddlers. Young ones are generally at greater risk than adults due to their limited sweating ability. In addition, their large skin surface relative to their small bodies and higher heat production from their activities add to their vulnerability.
In response to overheating, the human body perspires to cool down, mainly through the evaporation of sweat. When the air holds a significant amount of moisture, the efficiency of the evaporation process is decreased, preventing the body from cooling down efficiently, leading to the sensation of overheating. When body temperature rises due to an imbalance in heat gain, there's a potential for dehydration and overheating.

Humidity

The months with the lowest humidity in Polonnaruwa are June through September, with an average relative humidity of 67%.

Rainfall

In Polonnaruwa, in September, it is raining for 13.5 days, with typically 53mm (2.09") of accumulated precipitation. Throughout the year, there are 196.8 rainfall days, and 943mm (37.13") of precipitation is accumulated.

Daylight

The average length of the day in September is 12h and 10min.
On the first day of the month, sunrise is at 05:57 and sunset at 18:13. On the last day of September, in Polonnaruwa, Sri Lanka, sunrise is at 05:54 and sunset at 17:57 +0530.

Sunshine

The average sunshine in September is 10.9h.

UV index

The months with the highest UV index are February through October, with an average maximum UV index of 7. A UV Index of 6 to 7 symbolizes a high health risk from unprotected exposure to Sun's UV rays for the average person.
Note: In September, an average UV index of 7 transforms into the following instructions:
Enforce precautions and stick to sun safety measures. Preservation from skin and eye damage is essential. The time between 10 a.m. and 4 p.m. is when UV radiation is at its peak. Limit exposure to direct sunlight during these hours. Stay sun-safe with clothing that is both closely woven and worn loosely.