Last updated: August 28, 2025
September in Hanoi, Vietnam brings a mix of warmth and humidity, with temperatures soaring to a maximum of 37°C (99°F), while the average hovers around a comfortable 28°C (83°F). Nighttime offers a respite, dropping to a pleasant 21°C (71°F). This month is characterized by significant rainfall, accumulating to 222 mm (8.7 in) over 21 days, making it one of the wetter periods of the year. With an average humidity level of 82%, the air is thick and tropical, enhancing the city's vibrant atmosphere. Visitors should be prepared for sudden showers, but the lush scenery and lively streets offer a unique experience in this bustling capital.
As September unfolds in Hanoi, the city experiences a comforting shift in temperatures, marking a transition from the sweltering summer heat. With minimums averaging around 21°C (71°F) and maximums peaking at 37°C (99°F), visitors can enjoy a more temperate climate. The average temperature sits at a pleasant 28°C (83°F), offering a delightful respite after the intense summer months. This change not only invites exploration of the city's vibrant culture and stunning landscapes but also hints at the cooler days ahead in autumn, making September a perfect time for both locals and travelers to indulge in outdoor activities. The gradual decrease in nighttime temperatures adds a refreshing element, inspiring evening strolls along the bustling streets or by the tranquil lakes.
In September, Hanoi experiences a notable shift in its wet season, accumulating an average of 222 mm (8.7 in) of precipitation over 21 days. This marks a decrease from the heavy rainfall of August, which recorded 378 mm (14.9 in), yet still maintains the city's characteristic lush greenery. This transitional month signifies a balance between the high summer downpours and the approaching drier autumn. As the rains gradually ease, September is often marked by vibrant greenery and cooler temperatures, making it a picturesque time for residents and visitors alike to enjoy the renewed beauty of the city.
September in Hanoi, Vietnam, experiences a notable drop in humidity from the peak levels seen in the summer months, settling at an average of 82%. This slight decrease follows a sultry August, when humidity reached a steamy 89%, and precedes the more comfortable autumn days of October with a humidity of 77%. Throughout the year, humidity levels fluctuate, peaking in the height of summer with July hitting an impressive 90%. As the transition into fall begins, September's humidity still reflects the lingering tropical essence of the city, significantly higher than the winter months, which hover around the mid-60s to low-70s. This trend showcases Hanoi's shift from sweltering heat to a more pleasant atmosphere as the year progresses.
In September, Hanoi experiences a UV Index of 13, reflecting an extreme exposure category with a quick burn time of just 10 minutes. This trend, consistent with the preceding months of August and May, highlights a peak in solar radiation, underscoring the need for effective sun protection. Notably, the UV Index remains elevated throughout the summer, illustrating a gradual increase leading up to September, followed by a slight decrease in October. As such, it's crucial for residents and visitors alike to stay vigilant about sun safety during this time. For more details, you can explore the insights at Hanoi UV Index.
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As September rolls into Hanoi, the city basks in 267 hours of glorious sunshine, continuing a trend towards longer, sun-filled days that began in May. This month stands out, representing a delightful balance after the intense brightness of summer, where June and July boasted 275 and 274 hours respectively. The gradual transition from the sweltering months to the cooler autumn air is mirrored in the sunlight hours, showcasing a slight yet welcoming decrease from August's 259 hours. With the onset of September, residents and visitors alike can enjoy the warm glow of the sun, making it an ideal time to explore the vibrant streets and lush landscapes of Hanoi.
In September, Hanoi experiences a moderate 23% chance of sunny weather as the city transitions from the sweltering summer months to the more pleasant fall season. Compared to the preceding months, such as the notably gloomy July and August, which both see just 13% sunshine, September marks a slight but welcome improvement. While this percentage is lower than the sunny days found in the later months of the year like November (36%) and December (45%), it still presents a glimpse of brightness amidst the early autumn cloudiness. This mix of weather sets the stage for a charming and vibrant Hanoi, where the anticipation of clearer skies begins to rise.
As summer transitions to autumn, September in Hanoi offers a delightful balance of 12 hours of daylight—a slight dip from the peak of 13 hours experienced during the heart of summer. This change marks the beginning of shorter days, with daylight gradually decreasing as the year pushes toward its end. Notably, September retains the same amount of sunlight as both March and April, hinting at a sweet, lingering warmth before the cooler months set in. This transitional period invites residents and visitors alike to enjoy the city’s vibrant atmosphere under a canopy of golden light, bridging the gap between the lush exuberance of summer and the crispness of autumn.
As September arrives in Hanoi, the wind begins to whisper softly, with an average speed dipping to 1.5 m/s (3 mph). This gentle breeze marks a noticeable decline from the brisker months of spring and early summer, where winds reached heights of 2.8 m/s (6 mph) in May. After a summer of moderate air movement, September's calmness hints at the transition to the more invigorating winds of October, which surge back to 2.7 m/s (6 mph). This seasonal shift reflects not only the change in weather but also sets a tranquil backdrop for the city, inviting its residents and visitors to embrace the serene beauty of the early autumn days in Hanoi.
Weather in Hanoi varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Hanoi, focusing on differences in temperature, rainfall, humidity, and UV levels.
In September, the weather is characterized by warmer temperatures, with averages around 28°C (83°F) and maximums reaching up to 37°C (99°F). The month also sees significant rainfall, with 222 mm (8.7 in) spread over 21 days, contributing to a high humidity level of 82%. In contrast, January experiences much cooler conditions, with an average temperature of 18°C (65°F) and maximums of 29°C (84°F). Precipitation drops sharply to 58 mm (2.3 in) over just 8 days, and humidity decreases to 66%. For more details, you can check Hanoi weather in January.
When comparing the weather between September and February, the contrast is quite striking. September experiences much warmer temperatures, with minimums around 21°C (71°F) and maximums soaring up to 37°C (99°F), alongside high humidity levels of 82%. In contrast, February brings cooler conditions, with a minimum temperature of 9°C (48°F) and an average of 19°C (66°F), peaking at 31°C (88°F). Additionally, February sees significantly less precipitation, with only 41 mm (1.6 in) over about 7 days, compared to September's 222 mm (8.7 in) over 21 days. For a detailed look at the weather in February, you can check Hanoi weather in February.
September and March present contrasting weather patterns in terms of temperature and humidity. September is characterized by higher temperatures, with averages around 28°C (83°F) and peaks reaching up to 37°C (99°F), accompanied by significant rainfall of 222 mm (8.7 in) over 21 days and high humidity at 82%. In contrast, March offers a milder climate, with average temperatures of 22°C (73°F) and maximums around 34°C (94°F). The month is marked by much less precipitation, totaling only 65 mm (2.5 in) over 14 days and lower humidity at 69%. For more detailed insights about March weather, you can explore Hanoi weather in March.
September and April showcase distinct weather patterns. In September, temperatures range from a minimum of 21°C (71°F) to a maximum of 37°C (99°F), with an average of 28°C (83°F). This month also sees considerable rainfall, with 222 mm (8.7 in) over 21 days, contributing to a high humidity level of 82%. In contrast, April experiences milder temperatures, ranging from 15°C (59°F) to 36°C (97°F), with a pleasant average of 25°C (77°F). Precipitation is lower in April, totaling 147 mm (5.8 in) over 14 days and a more comfortable humidity level of 64%. For more detailed information, you can visit Hanoi weather in April.
September and May in Hanoi both feature warm average temperatures of 28°C (83°F), but September tends to experience slightly higher max temperatures of up to 37°C (99°F), while May can reach a peak of 39°C (103°F). Rainfall patterns differ as well, with September receiving more precipitation at 222 mm (8.7 in) over 21 days compared to May's 188 mm (7.4 in) over 17 days. Additionally, humidity levels are higher in September at 82%, contrasting with May’s lower humidity of 73%. For more detailed insights on May weather, check out Hanoi weather in May.
When comparing the weather in September and June, we see notable differences in both temperature and precipitation levels. September has a minimum temperature of 21°C (71°F) and an average of 28°C (83°F), while June presents a slightly higher minimum of 23°C (74°F) and an average temperature of 31°C (87°F). In terms of maximum temperatures, June can get quite hot, reaching up to 40°C (105°F), compared to September's high of 37°C (99°F). Rainfall is another significant factor; September experiences more precipitation with 222 mm (8.7 in) over 21 days, whereas June receives 189 mm (7.4 in) across just 15 days. Humidity levels are similar, with September at 82% and June slightly lower at 81%. For more detailed insights, you can check Hanoi weather in June.
In comparing the weather of September and July, September tends to be slightly cooler, with average temperatures ranging from a minimum of 21°C (71°F) to a maximum of 37°C (99°F), compared to July's warmer range from 25°C (78°F) to a peak of 39°C (103°F). However, September experiences more precipitation, with 222 mm (8.7 in) of rainfall across 21 days, though this is slightly less than the 260 mm (10.2 in) that July receives during the same number of days. Additionally, September's humidity is somewhat lower at 82%, in contrast to July's more humid conditions at 90%. For a detailed look at July weather specifics, you can visit Hanoi weather in July.
In comparing the weather between September and August, September exhibits slightly cooler temperatures with a minimum of 21°C (71°F) and an average of 28°C (83°F), compared to August's minimum of 24°C (76°F) and average of 29°C (85°F). While both months see high temperatures, August reaches a maximum of 39°C (102°F), which is higher than September’s peak of 37°C (99°F). Additionally, September receives about 222 mm (8.7 in) of precipitation over 21 days, while August is much wetter with 378 mm (14.9 in) across 22 days. The humidity is also marginally lower in September at 82% compared to 89% in August. For more detailed insights, refer to this link: Hanoi weather in August.
September and October in Hanoi showcase a noticeable shift in weather patterns. In September, temperatures range from a minimum of 21°C (71°F) to a sizzling maximum of 37°C (99°F), with an average of 28°C (83°F). This month also experiences significant rainfall, with 222 mm (8.7 in) falling over 21 days and high humidity at 82%. In contrast, October brings cooler temperatures, with a minimum of 17°C (63°F) and a maximum of 34°C (94°F), averaging 25°C (78°F). Precipitation increases to 279 mm (11.0 in) but occurs over fewer days, only 16, and the humidity drops slightly to 77%. For more detailed insights on October weather, visit Hanoi weather in October.
September and November offer distinctly different weather experiences. In September, temperatures are markedly higher, ranging from a minimum of 21°C (71°F) to a maximum of 37°C (99°F), accompanied by high humidity levels at 82%. This month also sees significant rainfall, with an average precipitation of 222 mm (8.7 in) spread over 21 days. In contrast, November brings cooler temperatures with a range from 14°C (57°F) to 33°C (92°F), less rainfall at just 48 mm (1.9 in), and fewer rainy days, totaling only 8. Additionally, humidity drops to a more comfortable 72%. For more detailed information on the weather in November, you can visit Hanoi weather in November.
In September, the weather is typically hot and humid, with temperatures ranging from a minimum of 21°C (71°F) to a maximum of 37°C (99°F), and an average temperature of 28°C (83°F). Rainfall is significant during this month, with 222 mm (8.7 in) of precipitation spread over 21 days, contributing to a high humidity level of 82%. In contrast, December brings a much cooler climate, with temperatures ranging from a minimum of 8°C (47°F) to a maximum of 31°C (87°F), and an average temperature of 18°C (65°F). Additionally, December sees far less precipitation, totaling only 41 mm (1.6 in) over 7 days, and the humidity drops to 71%. For more details on the weather during this month, check out Hanoi weather in December.
As September unfolds in Hanoi, the weather shifts towards a more humid and dynamic atmosphere, setting itself apart from the preceding months. The average temperature remains comfortably warm, yet the region experiences notable rainfall, with a significant rise in precipitation days compared to the dry summer. This increase in moisture contributes to the lush greenery that characterizes the city during this time, making it a picturesque period, albeit somewhat humid with high humidity levels. If you're planning a visit, be prepared for occasional downpours, but also enjoy the vibrant transformation of Hanoi's landscape. For a deeper dive into the seasonal trends, check out Hanoi Climate.