September weather forecastHanoi, Vietnam
September weather forecast for Hanoi, Vietnam: The average heat index, which factors the actual air temperature with the relative humidity, in September is evaluated at 43°C (109.4°F). August and September, with an average relative humidity of 80%, are the most humid months in Hanoi.

September
Weather in September
The weather in September brings about somewhat cooler temperatures compared to the previous summer months. Significantly, compared to August, precipitation decreases considerably to 73mm (2.87"). This dip in rainfall coupled with lower temperatures signifies the commencement of autumn. This cool and comfortably moist setting of September gradually progresses into October, bringing with it slightly cooler temperatures and reducing the volume of rain.Temperature
Hanoi, Vietnam, notes an average high-temperature of a still hot 31.7°C (89.1°F) in September, hardly diverging from August. During September, the temperature tends to dip to an average of 24.2°C (75.6°F) at night.Heat index
For most parts of September, the heat index is evaluated at an extremely hot 43°C (109.4°F). Stay mindful: Heat exhaustion and heat cramps are likely. Heatstroke could follow extended physical effort.Understand that the heat index values take into account shaded locations and mild winds. The heat index may scale up by 15 Fahrenheit (8 Celsius) degrees with direct sun exposure.
Note: The heat index, also known as 'apparent temperature' or 'feels like', gauges the sensation of temperature factoring in the air's moisture content. Elements such as metabolic variations, being pregnant, and physical activity can impact one's weather perception. Should you be directly under the sun, anticipate a possible increase in the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly important for children. Kids frequently fail to realize the necessity for resting and hydrating. Thirst is an advanced indication of dehydration - hence, maintaining hydration, especially during extended physical activities, becomes essential.
The physiological way the human body responds to excessive heat is by inducing perspiration, using sweat evaporation as a cooling mechanism. Elevated relative humidity disrupts typical body cooling by reducing the evaporation rate, consequently decreasing the body's cooling rate and enhancing the feeling of heat. Excessive heat gain, when not shed effectively by the body, can result in increasing body temperatures and related hazards.
Humidity
August and September, with an average relative humidity of 80%, are the most humid months in Hanoi.Rainfall
In Hanoi, Vietnam, in September, during 18.5 rainfall days, 73mm (2.87") of precipitation is typically accumulated. Throughout the year, in Hanoi, there are 181.2 rainfall days, and 595mm (23.43") of precipitation is accumulated.Daylight
In September, the average length of the day is 12h and 16min.On the first day of September, sunrise is at 05:40 and sunset at 18:12. On the last day of the month, sunrise is at 05:47 and sunset at 17:45 +07.
Sunshine
The average sunshine in September is 8.5h.UV index
May through September, with an average maximum UV index of 7, are months with the highest UV index. A UV Index estimate of 6 to 7 represents a high health vulnerability from exposure to the Sun's UV rays for the average person.Note: In September, an average UV index of 7 transforms into the following instructions:
Inhibit overexposure. Warding off sun damage is of utmost importance. Stay in the shade and avoid direct Sun exposure from 10 a.m. to 4 p.m., a period when UV radiation is particularly strong, noting that parasols or canopies may not offer total sun protection. To mitigate harm from sun exposure, pick sunglasses offering UVA and UVB defense.
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Hanoi, Vietnam
- Average high temperature in September: 31.7°C
The warmest month (with the highest average high temperature) is June (35.4°C).
The month with the lowest average high temperature is January (20.7°C).
- Average low temperature in September: 24.2°C
The month with the highest average low temperature is June (26.6°C).
The coldest month (with the lowest average low temperature) is January (14.4°C).
Average pressure in September
Hanoi, Vietnam
- Average pressure in September: 1008.5mbar
The month with the highest atmospheric pressure is January (1019.2mbar).
The month with the lowest atmospheric pressure is June (1003.1mbar).
Average wind speed in September
Hanoi, Vietnam
- Average wind speed in September: 6.9km/h
The windiest month (with the highest average wind speed) is March (9.9km/h).
The calmest months (with the lowest average wind speed) are August and September (6.9km/h).
Average humidity in September
Hanoi, Vietnam
- Average humidity in September: 80%
The months with the highest relative humidity are August and September (80%).
The month with the lowest relative humidity is December (69%).
Average rainfall in September
Hanoi, Vietnam
- Average rainfall in September: 73mm
The wettest month (with the highest rainfall) is August (135mm).
The driest month (with the least rainfall) is February (7mm).
Average rainfall days in September
Hanoi, Vietnam
- Average rainfall days in September: 18.5 days
The month with the highest number of rainy days is July (23.3 days).
The month with the least rainy days is February (7.8 days).
Average daylight in September /
Average sunshine in September
Hanoi, Vietnam
- Average daylight in September: 12h and 18min
The month with the longest days is June (Average daylight: 13h and 24min).
The month with the shortest days is December (Average daylight: 10h and 54min).
- Average sunshine in September: 8h and 30min
The month with the most sunshine is June (Average sunshine: 10h and 6min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).
Average sunshine days in September
Hanoi, Vietnam
- Average sunshine days in September: 9.5 days
The month with the most sunshine days is December (19.6 days).
The month with the least sunshine days is July (6.2 days).
Average UV index in September
Hanoi, Vietnam
- Average UV index in September: 7
The months with the highest UV index are May, June, July, August and September (UV index 7).
The month with the lowest UV index is December (UV index 4).
Average cloud cover in September
Hanoi, Vietnam
- Average cloud cover in September: 43
The month with the most cloud cover is January (Cloud cover 66).
The month with the least cloud cover is June (Cloud cover 40).
Average visibility in September
Hanoi, Vietnam
- Average visibility in September: 9km
The months with the highest visibility are February, March and June (10km).
The months with the lowest visibility are January, April, May, July, August, September, October, November and December (9km).





