September weather forecast
Hanoi, Vietnam

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

In September, Hanoi's weather conditions record an average high-temperature of a still hot 31.7°C (89.1°F), demonstrating little divergence from the preceding month. During the nights in September, Hanoi experiences a consistent average temperature of 24.2°C (75.6°F).

Heat index

In September, the heat index is estimated at a blistering 43°C (109.4°F). Forewarned: Heat cramps and heat exhaustion are anticipated. Ongoing physical activity increases the likelihood of heatstroke.
Research indicates the heat index considers values in shaded locales and with light winds. In the presence of direct sunshine, the heat index could be augmented by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'feels like' or 'felt air temperature', is an amalgamation of air temperature and humidity to express the equivalent perceived temperature. The individual's temperature perception can be influenced by numerous factors such as metabolic variations, physical activity, and clothing. In direct sunlight, the heat's impact can be heightened, potentially leading to an increase in the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly critical for babies and toddlers. In general, younger individuals are at greater risk than adults because they tend to sweat less. Also, having a larger skin surface to body size ratio and greater heat production due to their active behavior contribute to this danger.
By perspiring, the human body can shed its excessive warmth since evaporated sweat cools it off. When relative humidity is at high levels, the evaporation rate lessens, causing the body to keep more heat than it would in less humid conditions. Heat absorption that surpasses the body's shedding capability can lead to overheating and varying levels of dehydration.

Humidity

The months with the highest humidity in Hanoi are August and September, with an average relative humidity of 80%.

Rainfall

In Hanoi, during September, the rain falls for 18.5 days and regularly aggregates up to 73mm (2.87") of precipitation. In Hanoi, during the entire year, the rain falls for 181.2 days and collects up to 595mm (23.43") of precipitation.

Daylight

The average length of the day in September in Hanoi is 12h and 16min.
On the first day of the month, sunrise is at 05:40 and sunset at 18:12. On the last day of September, sunrise is at 05:47 and sunset at 17:45 +07.

Sunshine

The average sunshine in September in Hanoi is 8.5h.

UV index

The months with the highest UV index in Hanoi are May through September, with an average maximum UV index of 7. A UV Index reading of 6 to 7 represents a high health vulnerability from exposure to the Sun's UV rays for the ordinary person.
Note: In September, the maximum UV index of 7 suggests these recommendations:
Implement preventive steps and embrace sun safety standards. Protection from skin and eye distress is compulsory. Remember that the sun's UV radiation is strongest between 10 a.m. and 4 p.m. Make an effort to avoid direct sun exposure during these hours. For excellent sun protection for the eyes, ears, face, and neck, consider a wide-brim hat.