Last updated: August 21, 2025
September in Vientiane, Laos, showcases a tropical climate characterized by warm temperatures and significant rainfall. Daytime highs can reach a sweltering 37°C (98°F), while the average temperature hovers around 28°C (83°F), providing a warm yet humid experience. With nighttime lows falling to 23°C (73°F), the evenings offer a mild reprieve. This month also brings considerable precipitation, totaling 265 mm (10.4 in) over approximately 24 rainy days, contributing to a rather humid atmosphere with levels peaking at 86%. Visitors should prepare for a blend of warmth and moisture in this vibrant capital city.
In September, Vientiane experiences a pleasant transition toward cooler weather as temperatures begin to retreat from the peak summer heat. With minimums around 23°C (73°F), an average temperature of 28°C (83°F), and maximums peaking at 37°C (98°F), the month offers a blend of warmth and comfort. This slight decrease is consistent with the trend seen in the months following the summer highs, as the city moves toward a more moderate climate. Travelers and locals alike can enjoy outdoor activities amidst a backdrop of lush landscapes, making September an ideal time to explore the vibrant culture and natural beauty of Laos.
September in Vientiane, Laos, marks a significant transition in the annual precipitation pattern, with 265 mm (10.4 in) of rain recorded over 24 days. Following the peak of the monsoon in August, which boasts a staggering 402 mm (15.8 in), September sees a noticeable decline in rainfall but still remains quite substantial. This month is characterized by persistent showers that cultivate the lush landscapes of the region, bridging the wetter summer months to the drier autumn season. The gradual tapering of precipitation sets the stage for October's further decrease to 129 mm (5.1 in), illustrating the shift away from the relentless rains that define the preceding months. Overall, September remains crucial for replenishing local water sources while hinting at the imminent seasonal change ahead.
September in Vientiane, Laos, showcases a remarkable transition in humidity levels, maintaining a high average of 86%. This month is nestled within the rainy season, following the peak of 87% humidity seen in August. The trend from mid-year onward reveals a gradual increase in humidity, with May marking the shift towards more oppressive conditions, climbing from a mere 39% in March. As the monsoon rains continue, September remains notably humid compared to the drier months at the start of the year, such as January at 52% and February at 49%. This escalating humidity can create a notably warm and sticky environment, typical for the region as it embraces the wet season's full effects.
In September, Vientiane, Laos, continues to experience extreme UV index levels, peaking at 14, consistent with the preceding months of July and August. With a burn time of just 10 minutes, this high index highlights the urgent need for sun protection during outdoor activities. The enduring trend of elevated UV exposure from February through September emphasizes the importance of vigilance against skin damage, as the region transitions towards lower levels in October. For those planning their time in the sun, make sure to stay informed about the local conditions. For more details, check out the Vientiane UV Index.
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As September unfolds in Vientiane, Laos, it offers a delightful 275 hours of sunshine, marking a subtle resurgence after the summer months. While August tends to see the least sun with 249 hours, September signals a positive trend in daylight hours, bridging the monsoon's end and the onset of the more luminous fall. The sunshine steadily increases into October, where it reaches 295 hours, creating a beautiful transition highlighted by clear skies and vibrant sunsets. This month exemplifies a harmonious balance in Vientiane's climate, encouraging outdoor adventures and cultural explorations before the year draws to a close.
In Vientiane, Laos, the likelihood of sunny weather in September is notably low, sitting at just 17%. This marks a significant decline from the earlier months of the year, where January and February enjoy a robust 82% and 87% chance of sunshine, respectively. As the rainy season dominates from June through August, the opportunities for sunny days dwindle, plummeting to a mere 14% in August. While the sun does begin to peek back in October with a 30% chance, September remains one of the least sunny months, making it a time when travelers might want to prepare for overcast skies and rain showers rather than basking in the sun.
In September, Vientiane enjoys a pleasant 12 hours of daylight, continuing the trend seen throughout the preceding months of April to August. As summer transitions to autumn, daylight duration remains stable, reflecting a consistent pattern of longer days that peaks in June and July with a maximum of 13 hours. Following September, the hours of daylight will gradually begin to decrease, as the city shifts back to shorter days in autumn, ultimately settling at 11 hours by October. This rhythmic cycle not only enhances the beautiful landscapes of Laos but also marks the changing seasons in a region where daylight is a cherished part of daily life.
As September rolls into Vientiane, Laos, the gentle breezes bring a sense of calm, with an average wind speed of 1.5 m/s (3 mph). This month captures a notable trend in the year’s wind patterns, as it marks a gradual decline from the slightly stronger gusts experienced earlier in the wet season. Following the peak winds of January through July, September’s breezes feel softer, echoing the heavy rains of the previous months while paving the way for the upcoming cooler seasons. This trend of diminishing wind speed continues into October, suggesting a shift in the atmospheric rhythm as the region transitions towards drier months, making September a time for quiet reflection amidst the fluctuating weather.
Weather in Vientiane varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Vientiane, focusing on differences in temperature, rainfall, humidity, and UV levels.
September and January present stark contrasts in weather conditions. September boasts higher temperatures, with daily averages reaching 28°C (83°F) and maximums soaring up to 37°C (98°F). In this month, the humidity is high at 86%, accompanied by significant rainfall totaling 265 mm (10.4 in) over 24 days, making it one of the wettest months. In contrast, January sees a much cooler climate, with an average temperature of 24°C (75°F) and a maximum of 35°C (95°F). Precipitation drops dramatically to just 6 mm (0.2 in) over a single day, and humidity decreases to a more comfortable 52%. For more detailed insights, you can check out Vientiane weather in January.
September and February showcase striking contrasts in weather. September typically presents a warm climate with minimum temperatures around 23°C (73°F) and averages reaching 28°C (83°F), while highs can soar to 37°C (98°F). This month is also characterized by significant rainfall, averaging 265 mm (10.4 in) over 24 days, resulting in high humidity levels at 86%. In contrast, February offers a more temperate experience, with minimum temperatures of 13°C (55°F) and an average of 25°C (76°F), peaking at 38°C (100°F). Notably, February is much drier, with only 17 mm (0.7 in) of precipitation recorded across just a single day and a comfortable humidity of 49%. For more details on February's weather in Vientiane, you can refer to Vientiane weather in February.
In September, the weather in Vientiane is characterized by significantly higher humidity at 86%, alongside an average temperature of 28°C (83°F) and maximums reaching up to 37°C (98°F). This month also experiences considerable rainfall, with 265 mm (10.4 in) spread across 24 days, creating a quite wet and muggy atmosphere. In contrast, March offers a drier climate, with only 41 mm (1.6 in) of precipitation over just 6 days. The temperatures can soar to a maximum of 40°C (104°F), but the humidity drops to a more comfortable 39%, making it feel less oppressive than the wet season. For more information on March weather, check Vientiane weather in March.
September and April present notably different weather conditions. In September, temperatures range from a minimum of 23°C (73°F) to a maximum of 37°C (98°F), with an average of 28°C (83°F). September is also characterized by high humidity at 86% and considerable rainfall, totaling 265 mm (10.4 in) over 24 days. In contrast, April offers a slightly lower minimum temperature of 17°C (63°F), but can reach an impressive maximum of 42°C (107°F), with an average temperature of 29°C (85°F). Precipitation in April is significantly less, at only 70 mm (2.8 in) over 11 days and a much drier humidity level of 40%. For a detailed look at what to expect, check out Vientiane weather in April.
September and May showcase distinct weather patterns in terms of temperature and precipitation. In September, temperatures range from a minimum of 23°C (73°F) to a maximum of 37°C (98°F), while the average temperature is around 28°C (83°F). This month is characterized by heavy rainfall, with 265 mm (10.4 in) of precipitation over 24 days and high humidity levels at 86%. Conversely, May has slightly higher temperatures, with a minimum of 22°C (71°F) and a maximum of 41°C (107°F), leading to an average of 29°C (85°F). Rainfall is less intense, totaling 204 mm (8.0 in) over 21 days, and the humidity is notably lower at 69%. For more insights on May's weather, you can visit Vientiane weather in May.
In comparing the weather conditions of September and June, both months exhibit warm temperatures, but September tends to be slightly cooler on average. September features a minimum temperature of 23°C (73°F) and a maximum of 37°C (98°F), with an average of 28°C (83°F). In contrast, June has a higher minimum of 24°C (75°F) and a maximum of 39°C (102°F), averaging 29°C (85°F). Rainfall is more pronounced in June, with 309 mm (12.2 in) across 25 days, compared to September's 265 mm (10.4 in) over 24 days. While September has higher humidity levels at 86%, June is still quite humid at 81%. For more detailed insights, you can check the following link: Vientiane weather in June.
In comparing the weather of September and July, both months exhibit high temperatures, with September showing a minimum of 23°C (73°F) and an average of 28°C (83°F), while July starts slightly warmer with a minimum of 25°C (76°F) and an average of 29°C (84°F). Despite the similar maximum temperatures peaking at 37°C (98°F in September and 99°F in July), September experiences more rainfall, accumulating 265 mm (10.4 in) over 24 days compared to July’s 331 mm (13.0 in) over 26 days. Additionally, September's humidity is marginally higher at 86%, whereas July maintains a comfortable 83%. For a more detailed look at July's conditions, you can refer to Vientiane weather in July.
In comparing the weather of September and August, both months share similar temperature ranges, with average highs reaching up to 37°C (98°F) and lows around 23-24°C (73-75°F). However, September experiences significantly less precipitation, with 265 mm (10.4 in) over 24 days, compared to August's 402 mm (15.8 in) over 26 days. Humidity levels remain high in both months, with September at 86% and August slightly higher at 87%. For more detailed insights, you can check Vientiane weather in August.
September is characterized by warmer temperatures, with minimums around 23°C (73°F) and maximums reaching up to 37°C (98°F). This month experiences significant rainfall, averaging 265 mm (10.4 in) over 24 days, creating a humid environment with humidity levels around 86%. In contrast, October offers a slight cooling trend, with minimum temperatures dropping to 20°C (68°F) and maximums peaking at 36°C (98°F). The precipitation also decreases significantly to 129 mm (5.1 in) across 15 days, leading to lower humidity levels at 74%. This shift marks a transition towards drier conditions as the weather cools, making October more pleasant. For a detailed look at conditions during this month, check out Vientiane weather in October.
In September, the weather is characterized by higher temperatures and significant humidity, with minimums around 23°C (73°F) and average highs peaking at 37°C (98°F). The month experiences considerable rainfall, totaling 265 mm (10.4 in) over 24 days, leading to a steamy atmosphere with humidity levels reaching 86%. In contrast, November sees a noticeable drop in both temperature and humidity, with minimums around 17°C (63°F) and average highs of 36°C (98°F). Precipitation is minimal, averaging only 10 mm (0.4 in) across just 3 days, resulting in a drier and more comfortable climate. For further details, you can check Vientiane weather in November.
September and December showcase a dramatic shift in weather patterns. In September, temperatures soar with minimums around 23°C (73°F) and highs reaching a sweltering 37°C (98°F), accompanied by significant rainfall of 265 mm (10.4 in) over 24 days, creating a humid atmosphere with 86% humidity. In contrast, December offers a much milder climate, featuring minimum temperatures of 9°C (48°F) and average highs of 35°C (95°F), while precipitation drops significantly to just 7 mm (0.3 in) over only 1 day, resulting in a much drier and less humid environment with 57% humidity. For those interested in the specifics of December's weather, more information can be found here: Vientiane weather in December.
As September unfolds in Vientiane, it brings a unique twist to the region's climate. This month sees a significant increase in humidity, reaching a notable 86%, which often makes the warm temperatures feel even more intense. Although maximum temperatures can soar up to 37°C (98°F), the frequent precipitation, with about 24 days of rainfall accumulating to 265 mm (10.4 in), sets this month apart from the drier summer months. This combination of warmth and moisture transforms September into a lush and vibrant season, perfect for those looking to experience Vientiane's rich, tropical beauty. For a more detailed overview of the climate, check out Vientiane Climate.