September weather forecast and climate
Mumbai, India

The last month of the rainy (monsoon) season, September, is a hot month in Mumbai, India, with average temperature fluctuating between 30.4°C (86.7°F) and 24.3°C (75.7°F).

Temperature

In Mumbai, the average high-temperature is essentially the same as in August - a tropical 30.4°C (86.7°F). In Mumbai, the average low-temperature is 24.3°C (75.7°F).

Heat index

The average heat index in September is calculated to be a sweltering 39.9°C (103.8°F). Take extra precautions, as heat cramps and heat exhaustion are possible. Sustained activity may result in heatstroke.
Note that heat index values are valued for light wind and location in the shade. With exposure to direct sunlight, the heat index may be increased by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like', 'apparent temperature', 'real feel', or 'felt air temperature', is a measure that combines air temperature and relative humidity into a single value that indicates how hot the weather feels. Additional factors like activity, metabolic differences, differences in body mass, height, and shape, and wind affect individual temperature impact. 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 particularly important for children. Children are often less aware of the need to rest and re-hydrate. Thirst is a late sign of dehydration - it is vital to remain hydrated, particularly during prolonged physical activities.
The human body normally cools itself by perspiration. Excessive warmth is eliminated from the body by evaporation of sweat. A higher relative humidity affects normal body cooling by reducing the evaporation rate, subsequently lowering the rate at which the body cools and increasing the perception of heat. 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 Mumbai, the average relative humidity is 83%.

Rainfall

In Mumbai, during 14.4 rainfall days, 312.3mm (12.3") of precipitation is typically accumulated. Throughout the year, there are 78.9 rainfall days, and 2258mm (88.9") of precipitation is accumulated.

Sea temperature

In September, the average sea temperature in Mumbai, India, is 28.7°C (83.7°F).
Note: 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.

Daylight

In September, the average length of the day in Mumbai is 12.2h.

Sunshine

In September, the average sunshine in Mumbai is 5.5h.

UV index

Months with the highest UV index are March through September, with an average maximum UV index of 12. A UV Index value of 11, and more, symbolizes an extreme threat to health from unprotected exposure to the Sun's UV rays for average individuals.
Note: In September, the average maximum UV index of 12 translate into the following recommendations:
Practice all-important precautions. Light skin people may get burned in less than 5 minutes. 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. 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. A broad-spectrum sunscreen of SPF 30+ should be liberally applied and re-applied every two hours, and immediately after an outdoor workout or a swim. Caution! The reflection of sand and water significantly increases the intensity of the Sun's UV radiation.