September Weather in Ulan Bator, Mongolia

Last updated: August 28, 2025

September in Ulan Bator, Mongolia presents a striking transition toward autumn, characterized by maximum temperatures reaching 27°C (81°F) and an average of 9°C (48°F). Daily life is influenced by cooler evenings, with temperatures dipping to a brisk minimum of -9°C (16°F). The city's weather during this month also brings 51 mm (2.0 in) of precipitation over approximately 8 days, resulting in a humidity level of 65%. These dynamic conditions create a unique atmosphere, inviting both locals and travelers to experience the changing season in this vibrant capital.

September Temperature in Ulan Bator

In September, Ulan Bator transitions gracefully from the warmth of summer into the crisp embrace of autumn. The average temperature hovers around 9°C (48°F), reflecting a notable cool down from the previous months. Nighttime lows dip to -9°C (16°F), as the city prepares for the colder months ahead. However, the daytime still offers a pleasant warmth, with highs reaching up to 27°C (81°F), making it an ideal time for outdoor exploration. As the days become shorter and the air turns crisp, September serves as a gentle reminder of the approaching winter, while still allowing residents and visitors to enjoy the last vestiges of warmth before the chill sets in.

September Weather in Ulan Bator: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Ulan Bator, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Ulan Bator, September typically has an average temperature of {2}°C ({3}°F), with highs reaching up to {4}°C ({5}°F) and lows dropping to around {6}°C ({7}°F).
JanFebMarAprMayJunJulAugSepOctNovDec-8-1203648596358483011-6
Data source: Temperature data for Ulan Bator generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Ulan Bator

September marks a notable transition in Ulan Bator's precipitation patterns, with 51 mm (2.0 in) of rain falling over an average of 8 days. This amount represents a significant drop from August’s peak of 83 mm (3.3 in), yet it remains the second-highest monthly total of the latter half of the year. As summer wanes, the frequency of rainfall continues to reflect a diminishing trend, with October typically bringing even lower totals. Despite this decrease, September’s rainfall serves as a crucial buffer, nourishing the landscape as it shifts into the cooler autumn months ahead. The shift from the rainy peak of midsummer to the moderate autumn precipitation sets the stage for Ulan Bator's climatic transition, highlighting the region's extremes.

September Precipitation Trends in Ulan Bator

The chart displays monthly precipitation patterns in Ulan Bator, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In Ulan Bator, September typically receives around {2} mm ({3} inches) of precipitation spread over approximately {4} days.
JanFebMarAprMayJunJulAugSepOctNovDec25715264472835121103
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Ulan Bator

As autumn approaches in Ulan Bator, September's humidity levels rise to 65%, a slight increase from the milder summer months where humidity hovered around 57% to 58%. This transitional month marks a shift from the drier conditions of May and June, which recorded their lowest levels of about 50%. Notably, September's humidity is on par with October's, suggesting a trend of relatively stable moisture levels as the city prepares for the colder months ahead. As winter looms, humidity will climb further to 67% in November and 89% by December, highlighting a persistent increase as the year draws to a close. With these shifts, September serves as a pivotal moment in Ulan Bator's climatic rhythm, bridging the dry warmth of summer with the icy grip of winter.

September Average Humidity in Ulan Bator

This chart illustrates the average monthly humidity levels in Ulan Bator, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Ulan Bator is approximately {2}%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec92%84%64%59%50%55%57%58%65%65%67%89%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Ulan Bator

In September, Ulan Bator experiences a notable shift in its UV Index, registering at 6—a decrease from the summer months but still categorized as high. This means that while the harsh summer sun begins to wane, outdoor enthusiasts should remain vigilant, with a burn time of 25 minutes before sun protection becomes essential. The trend from early in the year shows a gradual rise in UV exposure, peaking at a very high level during the summer months of May through August, where the UV Index consistently stayed at 9. As autumn approaches in October, the UV Index drops further, indicating a transition to more moderate sun exposure. For more detailed information, check out the Ulan Bator UV Index.

Maximum UV Index Levels in Ulan Bator for September

The chart shows the monthly maximum UV Index (UVI) for Ulan Bator in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in Ulan Bator typically reaches {2}, which falls under the {3} exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec235799996431
Data source: Ulan Bator September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

September Sunshine in Ulan Bator

As the calendars turn to September, Ulan Bator basks in a remarkable 311 hours of sunshine, continuing its pattern of brightening days. Following the summer months, which peak with July's 373 hours, September's warmth signals a graceful transition into autumn. Despite a subtle decline from August's 346 hours, the sunlight remains abundant, reflecting the city's vibrant energy as it prepares for the cooler months ahead. With the daylight hours gradually waning, September offers a beautiful blend of lingering summer warmth and the crisp promise of fall, making it a captivating time to experience Ulan Bator's dynamic landscape.

Monthly Sunshine Duration in Ulan Bator: September Highlighted

The September sunshine duration represents the total number of hours Ulan Bator experiences direct sunlight during the month of September, excluding cloudy or obstructed periods. This chart compares the sunshine duration of September with the other months of the year.
JanFebMarAprMayJunJulAugSepOctNovDec203h265h327h333h376h369h373h346h311h294h263h250h
Data source: Ulan Bator September Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Ulan Bator During September

In Ulan Bator, September marks a noteworthy transition in the weather patterns as the chance of sunny days rises to 51%. This slight increase in sunshine compared to the summer months, where the chances linger around 41%, suggests a welcomed shift as the region gears up for autumn. Although still lower than the clearer skies of October, which boasts a 69% chance of sun, September offers a refreshing balance of lingering warmth and the crispness of the fall season. As daylight begins to wane, this month serves as a beautiful bridge between the sun-drenched days of summer and the brighter, clearer skies that follow.

Percentage of Sunny Days in September in Ulan Bator

The chart illustrates the percentage of sunny days in Ulan Bator throughout the year, with September highlighted. It highlights the variation in sunshine across each month and provides an overview of the typical frequency of sunny days, offering insights into how often Ulan Bator experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec44%58%55%53%45%41%41%44%51%69%65%75%
Data source: Ulan Bator September chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Ulan Bator in September

In Ulan Bator, Mongolia, the daylight duration showcases a clear seasonal rhythm as the year progresses. September marks a gentle transition, with 12 hours of daylight, a decrease from the peak of 15 hours seen during the summer months of June and July. As autumn approaches, the city starts to experience shorter days, following a gradual decline that began in August. This ongoing shift reminds residents of the impending winter, as daylight will continue to wane, reducing to just 8 hours by January. The pattern exhibits a vibrant dance of light, illustrating the unique beauty of Mongolia's changing seasons.

Average Daylight Hours in Ulan Bator for September

The chart illustrates the variation in daylight duration in Ulan Bator throughout the year, with September highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec8h 51m10h 12m11h 54m13h 39m15h 9m15h 56m15h 32m14h 12m12h 32m10h 48m9h 15m8h 26m
Data source: Ulan Bator daylight hours, calculated by summing the hours between sunrise and sunset for each day.

September Winds in Ulan Bator

As September arrives in Ulan Bator, the city experiences a gentle breeze with an average wind speed of 2.6 m/s (6 mph), mirroring the calmness of its early winter months. This slight uptick from the summer's 2.3 m/s (5 mph) in July suggests a transition, as the winds are noticeable yet not overpowering. The wind speeds show an interesting trend throughout the year, with a modest rise in the spring to a peak of 3.8 m/s (9 mph) in May, before tapering off as the seasons shift. By September, the winds are just enough to carry the crispness of autumn, setting a serene backdrop for the stunning changes in Ulan Bator's landscape. As the year progresses, September's winds hint at the impending chill of winter, creating an atmosphere that is both refreshing and tranquil.

Average September Wind Speed in Ulan Bator

The chart displays monthly wind speed patterns in Ulan Bator, with values for each month shown alongside September's data, which is highlighted for easy comparison. It illustrates the average wind speed, offering insights into how September's wind conditions compare to the rest of the year.
JanFebMarAprMayJunJulAugSepOctNovDec2.62.43.13.43.83.32.32.92.6 m/s2.52.52.4
Data source: Ulan Bator September wind data, generated using information from the Copernicus Climate Change Service.

How September Weather in Ulan Bator Compares to Other Months

Weather in Ulan Bator varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Ulan Bator, focusing on differences in temperature, rainfall, humidity, and UV levels.

September and January present strikingly contrasting weather conditions. In September, temperatures range from a chilly minimum of -9°C (16°F) to a pleasant average of 9°C (48°F), peaking at a warm 27°C (81°F). The month sees some precipitation, totaling 51 mm (2.0 in) over about 8 days, with a moderate humidity level of 65%. In contrast, January's conditions are far more severe, with temperatures plummeting to a frigid minimum of -42°C (-44°F) and an average temperature of -22°C (-8°F), not exceeding a maximum of -5°C (23°F). This month experiences very little precipitation—only 2 mm (0.1 in)—and boasts humidity levels rising to a notable 92%. For more details, visit the link: Ulan Bator weather in January.

In comparing the weather between September and February, significant differences are evident. September typically sees much milder temperatures, with average highs around 27°C (81°F) and lows of -9°C (16°F), making it a transitional month as summer fades. In contrast, February experiences harsh cold, with average temperatures plummeting to -18°C (0°F) and daily highs rarely reaching above freezing, peaking at only 4°C (39°F). Furthermore, September receives more precipitation, averaging 51 mm (2.0 in) over 8 days, while February is notably drier, with just 5 mm (0.2 in) over 1 day. Humidity levels in February are higher at 84%, compared to the more moderate 65% in September, adding to the overall chill of the winter month. For those looking for more detailed information, you can check out the Ulan Bator weather in February.

When comparing the weather in September and March, the differences are stark. September boasts a milder temperature range, with minimums of -9°C (16°F) and maximums reaching up to 27°C (81°F), averaging around 9°C (48°F). In contrast, March experiences much colder conditions, with minimum temperatures plummeting to -29°C (-20°F) and maximums only climbing to 16°C (61°F), resulting in an average of -7°C (20°F). Additionally, precipitation is more common in September, with 51 mm (2.0 in) over 8 days, whereas March sees a mere 7 mm (0.3 in) over just 2 days. Both months have similar humidity levels, hovering around 65% in September and 64% in March. For a closer look at March weather, you can check Ulan Bator weather in March.

Comparing the weather in September and April reveals notable differences in temperature, precipitation, and humidity. In September, temperatures range from a minimum of -9°C (16°F) to a maximum of 27°C (81°F), with an average around 9°C (48°F). The month experiences 51 mm (2.0 in) of precipitation over approximately 8 days, contributing to a humidity level of 65%. In contrast, April has cooler conditions, with temperatures dipping from a minimum of -16°C (4°F) to a maximum of 25°C (77°F), and an average of just 2°C (36°F). The precipitation in April is significantly lower at 15 mm (0.6 in), occurring on about 4 days, with a humidity level of 59%. For a more detailed look at April weather, check out Ulan Bator weather in April.

In comparing the weather between September and May, we see a notable difference in temperature and precipitation patterns. September experiences a wider temperature range, with minimums dipping to -9°C (16°F) and maximums reaching 27°C (81°F), while May has a slightly milder range with minimums at -8°C (18°F) and maximums peaking at 30°C (87°F). Additionally, September sees more rainfall, with an average of 51 mm (2.0 in) over 8 days, compared to May's lighter precipitation of 26 mm (1.0 in) over just 5 days. Humidity levels also vary, as September averages 65%, making it a bit more humid than May, which holds a lower average of 50%. For more detailed information on May weather specifically, you can check Ulan Bator weather in May.

September weather in Ulan Bator exhibits a more varied temperature range compared to June, with minimums dipping to -9°C (16°F) and maximums reaching up to 27°C (81°F). The average temperature in September is 9°C (48°F), while June enjoys warmer conditions with averages around 15°C (59°F) and highs reaching 32°C (90°F). Additionally, September experiences slightly more precipitation at 51 mm (2.0 in) over 8 days, compared to June's 44 mm (1.7 in) over 7 days. Humidity levels also differ, with September being more humid at 65%, compared to June's 55%. For a more detailed look at June conditions, visit Ulan Bator weather in June.

September and July present notable differences in weather patterns. In September, temperatures range from a chilly minimum of -9°C (16°F) to a comfortable maximum of 27°C (81°F), averaging around 9°C (48°F). In contrast, July enjoys warmer temperatures, with a minimum of 5°C (41°F) and a maximum of 32°C (91°F), resulting in an overall average of 17°C (64°F). Precipitation levels also vary, as September experiences 51 mm (2.0 in) over about 8 days, while July sees more rainfall at 72 mm (2.9 in) across 12 days. Additionally, September has a higher humidity level at 65% compared to July's 57%. For more detailed insights, you can check Ulan Bator weather in July.

In comparing the weather of September and August, we observe notable differences in temperature and precipitation patterns. September experiences a broader temperature range, with minimums dropping to -9°C (16°F) and maximums peaking at 27°C (81°F), resulting in an average of 9°C (48°F). In contrast, August maintains milder temperatures, with minimums at 0°C (33°F) and maximums reaching 28°C (82°F), yielding an average of 14°C (58°F). Additionally, September sees less precipitation than August, with 51 mm (2.0 in) of rainfall over 8 days compared to 83 mm (3.3 in) over 13 days in August. The humidity is also slightly higher in September at 65% compared to August's 58%. For more detailed information, you can check Ulan Bator weather in August.

September and October present a stark contrast in weather conditions. In September, temperatures range from a minimum of -9°C (16°F) to a balmy maximum of 27°C (81°F), averaging around 9°C (48°F). The month features around 51 mm (2.0 in) of precipitation over about 8 days, maintaining a humidity level of 65%. In contrast, October sees much colder temperatures with a minimum of -16°C (4°F) and an average temperature dropping to -1°C (30°F), though it can still reach up to 22°C (72°F) at its highest. October produces significantly less precipitation at 21 mm (0.8 in) over just 4 days, yet still holds the same humidity level at 65%. For a more detailed look at conditions, visit Ulan Bator weather in October.

September and November present stark contrasts in weather conditions. In September, temperatures range from a minimum of -9°C (16°F) to a maximum of 27°C (81°F), with an average of 9°C (48°F). The month experiences 51 mm (2.0 in) of precipitation over 8 days, accompanied by a humidity level of 65%. By November, the landscape shifts dramatically as temperatures drop significantly, with a minimum of -35°C (-32°F) and an average of -12°C (11°F), peaking at a mere 9°C (49°F). Precipitation decreases to just 10 mm (0.4 in) over only 2 days, and humidity rises slightly to 67%. For more specific insights on November's conditions, you can visit Ulan Bator weather in November.

In comparing the weather between September and December, it is clear that they differ significantly. September boasts a broader temperature range, with minimums around -9°C (16°F) and maximums reaching 27°C (81°F), resulting in a mild average of 9°C (48°F). This month also experiences moderate precipitation at 51 mm (2.0 in) over about 8 days, coupled with a humidity level of 65%. In stark contrast, December brings harsher winter conditions, with temperatures plummeting to a minimum of -39°C (-38°F) and an average of -21°C (-5°F), while the maximum temperatures barely reach -3°C (28°F). The precipitation decreases significantly to just 3 mm (0.1 in) across the month, with no recorded rainy days, and humidity rises to 89%, creating a crisp, dry cold. For more details on December weather in Ulan Bator, you can visit Ulan Bator weather in December.

Compare Ulan Bator's Climate with Cities Worldwide

Conclusion: What to Expect From September Weather in Ulan Bator

September in Ulan Bator marks a notable transition in weather as the city moves from the warmth of summer into the cool embrace of autumn. With average temperatures dipping to a crisp 9°C and occasional peaks reaching 27°C, it's a time when the cool air begins to set in, especially with nighttime lows falling to around -9°C. While rainfall is moderate, with around 51 mm falling over approximately 8 days, humidity levels hover around 65%, lending an invigorating freshness to the air. This month stands out, offering a unique blend of warm days and cool evenings, making it a delightful time for outdoor exploration. For a deeper understanding of what to expect throughout the year, check out the detailed insights on Ulan Bator Climate.