September weather forecast
Jakarta, Indonesia

September marks a transition period in Jakarta's weather, as the dry season begins to give way to the rainy season. The rainfall sees a steady increase from 35mm (1.38") in August to 46mm (1.81"). Despite this, the city's weather remains predominantly dry, with only a slight uptick in the number of rainy days. Variations in the temperatures, sea temperature, wind speeds, and pressure remain within minor ranges, signaling stable weather conditions. Come September, sun enthusiasts still relish the extended sunshine hours, while rainfall begins to gradually saturate the terrain.

Temperature

Entering September in Jakarta, the average high-temperature is recorded at a still tropical 31.2°C (88.2°F), exhibiting a minimal shift from August's 31.1°C (88°F). Jakarta records an average nighttime low-temperature of 25°C (77°F) throughout September.

Heat index

For most parts of September, the heat index is calculated to be a fiery hot 38°C (100.4°F). Take greater precautions, heat exhaustion and heat cramps may be expected. Heatstroke could result from lengthy activity.
One should consider that heat index numbers are for shaded settings and light wind. When under direct sunshine, the heat index may be elevated by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature' or 'feels like', marries air temperature and humidity to produce a value illustrating perceived warmth. An individual's perception of weather can be affected by a variety of elements including metabolic differences, being pregnant, and their level of physical exertion. It is noteworthy that being in direct sunlight can enhance the weather's impact, raising the heat index by as much as 15 Fahrenheit (8 Celsius) degrees. Heat index values are largely significant for babies and toddlers. Typically, children face more danger than adults as they usually perspire less. Their larger skin surface relative to their small bodies and increased heat output from their activities enhance their risk.
When it comes to cooling down, the human body's primary method is through perspiration, making use of sweat evaporation to eliminate excess heat. In the presence of high relative humidity, the evaporation rate diminishes, resulting in the body retaining more warmth compared to dry conditions. Overheating and dehydration threats arise when heat gain goes beyond what the body can comfortably shed.

Humidity

The average relative humidity in September is 68%.

Rainfall

In September, in Jakarta, the rain falls for 13.5 days. Throughout September, 46mm (1.81") of precipitation is accumulated. In Jakarta, during the entire year, the rain falls for 252 days and collects up to 1150mm (45.28") of precipitation.

Sea temperature

In September, the average sea temperature in Jakarta, Indonesia, is 29°C (84.2°F).
Note: With water temperature from 25°C (77°F) to 29°C (84.2°F), all water activities are comfortable and delightful, devoid of discomfort even for lengthened periods.

Daylight

The average length of the day in September in Jakarta is 12h and 4min.
On the first day of September, sunrise is at 05:52 and sunset at 17:52. On the last day of the month, sunrise is at 05:37 and sunset at 17:47 WIB.

Sunshine

In Jakarta, Indonesia, the average sunshine in September is 9.6h.

UV index

The months with the highest UV index in Jakarta, Indonesia, are January through December, with an average maximum UV index of 7. The months with the lowest UV index are January through December, with an average maximum UV index of 7. A UV Index estimate of 6 to 7 represents a high health risk from unprotected exposure to Sun's UV rays for the average person.
Note: In September, a daily UV index of 7 turns into the following recommendations:
Sidestep overexposure. Individuals with fair complexions risk burning in fewer than 20 minutes. From 10 a.m. to 4 p.m., when UV radiation is at its strongest, limit direct exposure to the Sun and note that shade structures may not provide full sun protection. Using UVA and UVB-protective sunglasses and sun-protective clothing is effective against UV radiation. Be mindful! Sand and water reflections can up the Sun's UV exposure.