Last updated: October 30, 2025
Experience the vibrant September weather in Osan, South Korea, where the average temperature hovers around 22°C (71°F), with a peak reaching a warm 31°C (88°F). As summer transitions to autumn, temperatures can dip to a cooler 9°C (48°F) at night, offering a delightful mix of warmth and brisk air. Expect 136 mm (5.4 inches) of rainfall spread over approximately 9 days, contributing to the city's lush landscapes. With an average humidity level of 77%, the air carries a hint of freshness, making September an ideal time to explore Osan's rich culture and natural beauty.
In September, Osan, South Korea, experiences a notable shift towards milder temperatures as summer transitions into autumn. The month showcases a minimum temperature of 9°C (48°F), allowing for refreshing coolness during the nights, while the average daily temperature hovers at a comfortable 22°C (71°F). As the days continue to warm, the maximum temperatures can reach up to 31°C (88°F), yet the intense heat of the preceding months begins to recede, marking a delightful reprieve. This gradual cooling signals the onset of fall, providing a perfect backdrop for outdoor activities amidst the colorful landscape that autumn brings to the region. Overall, September offers a harmonious blend of warm days and cooler nights, ideal for enjoying all that Osan has to offer.
September in Osan, South Korea, marks a notable shift in precipitation patterns, bringing 136 mm (5.4 in) of rain over 9 days. This figure reveals a significant decrease compared to the previous months' torrential downpours, particularly July and August, which saw 235 mm (9.3 in) and 255 mm (10.1 in) respectively. As summer transitions into autumn, the frequent rainfall begins to taper, showing a more moderate climate. September's precipitation reflects the end of the monsoon influence, as the region prepares for drier conditions ahead, with only 62 mm (2.5 in) expected in October. This pattern underscores the gradual shift from the heavy rains of summer to the more subdued and balanced precipitation typically characteristic of fall in Osan.
September in Osan, South Korea, marks a transition from the sweltering summer months, where humidity peaks at a staggering 91% in both July and August. As the seasons shift, the humidity begins to ease, settling at 77% this month. This decline signals the onset of autumn, yet it remains higher than the winter averages, highlighting a distinct trend of elevated humidity levels throughout the warmer months. Following September, humidity levels hover around 79% in October and 80% in November, indicating a gradual adjustment towards the cooler, drier air of winter. As such, residents experience a noticeable change in comfort as the summer's oppressive humidity recedes, paving the way for a refreshing fall season.
As September rolls in, the UV Index in Osan, South Korea, remains notably high at 9, categorized as very high exposure. This marks a gradual decline from the peak index of 11 experienced in July and August but still requires caution for sun-seekers, as unprotected skin can burn in just 15 minutes. The trend across the months showcases a shift from moderate exposure in the winter months to extreme levels during summer, with the UV Index peaking in mid-year before tapering off into autumn. As the days shorten and temperatures cool, sun protection remains vital until the UV Index drops further in October. For detailed insights, check the Osan UV Index.
UV Risk Categories
As September dawns in Osan, South Korea, the city begins to embrace the golden hues of autumn while still basking in the warmth of its late-summer sunshine. With 261 hours of sunlight, September marks a slight dip from the vibrant summer months but continues to outshine the earlier winter and spring. As the days gradually shorten, it's evident that the summer’s peak hours in May and June, averaging around 315 and 318 hours, set a warm precedent for the shifting seasons. This change is not just a countdown to colder months but a beautiful transition where the soft, mellow light invites residents and visitors alike to enjoy the lingering outdoor adventures before the brisk chill of fall settles in.
In Osan, South Korea, September experiences a 39% chance of sunny weather, marking a slight increase from the summer months, which grapple with lower averages of 30% to 31% in July and August. This month acts as a transitional period, where the lingering warmth of late summer begins to fade, subtly enhancing the likelihood of clearer skies. As the year progresses, the odds of sunshine improve significantly; for comparison, October sees a notable rise to 47%, indicating a trend towards brighter days as autumn sets in. Therefore, while September may not offer the sunniest days, it holds potential for pleasant weather, foreshadowing the clearer skies that follow in the subsequent months.
As September rolls in, Osan, South Korea, experiences a gentle transition in daylight duration, with the average hours of sunlight reaching 12 hours. This marks a subtle decline from the 14 hours enjoyed during the peak summer months of June through August. The gradual decrease in daylight reflects the seasonal shift towards autumn, where longer evenings encourage cozy gatherings and outdoor activities under the fading light. Following September, daylight hours will continue to wane, dipping further to 11 hours in October and 10 hours in November, ushering in the chillier months ahead. This progression highlights the rhythmic nature of the seasons, making each changing month a unique experience in Osan.
As summer transitions to autumn, September in Osan brings a gentle breeze, with an average wind speed of 2.7 m/s (6 mph). This slight increase from the summer lows reflects a gradual shift in the weather pattern, as the city begins to cool down. Compared to the calmer months of July and August, where winds dipped to their annual lows of 2.0 m/s (4 mph) and 2.3 m/s (5 mph) respectively, September reintroduces a refreshing air movement that hints at the upcoming fall season. This marks a resurgence in wind strength, reminiscent of the early spring months, suggesting that Osan is ready to embrace the vibrant changes autumn brings. With the winds picking up, September is a delightful reminder of nature's rhythm as it prepares for the crisp days ahead.
Weather in Osan varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Osan, focusing on differences in temperature, rainfall, humidity, and UV levels.
September and January present striking contrasts in weather. In September, temperatures range from a minimum of 9°C (48°F) to a maximum of 31°C (88°F), with an average of 22°C (71°F). The month is characterized by significant rainfall, totaling 136 mm (5.4 in) over about 9 days, contributing to a higher humidity level of 77%. In contrast, January sees much colder conditions, with temperatures dipping to a minimum of -17°C (2°F) and averaging -2°C (29°F), peaking at a maximum of 13°C (55°F). Precipitation is markedly lower in January, totaling just 21 mm (0.8 in) across 2 days, and the humidity drops slightly to 71%. For more details on January weather, you can visit Osan weather in January.
September and February present starkly different weather patterns. In September, temperatures range from a mild 9°C (48°F) at night to a warm average of 22°C (71°F), peaking at a high of 31°C (88°F). The month also sees considerable precipitation, with 136 mm (5.4 in) falling over about 9 days, and humidity averaging a humid 77%. In contrast, February brings a much colder climate, with temperatures dipping as low as -15°C (4°F) during the night and averaging around 0°C (33°F). The high for February reaches only 18°C (65°F), and it experiences significantly less precipitation, totaling 23 mm (0.9 in) over just 4 days, accompanied by lower humidity levels at 65%. For a closer look at the February weather specifics, you can visit Osan weather in February.
In September, the weather tends to be much warmer, with temperatures ranging from a minimum of 9°C (48°F) to a maximum of 31°C (88°F) and an average of 22°C (71°F). This month also experiences higher humidity at 77% and significant rainfall, with 136 mm (5.4 in) over approximately 9 days. In contrast, March ushers in cooler temperatures, with a minimum of -6°C (21°F), an average of 7°C (44°F), and a maximum of 21°C (70°F). Precipitation is considerably lower during this month, totaling only 47 mm (1.9 in) over about 5 days, and humidity also decreases to 65%. For more details on the weather in March, you can visit Osan weather in March.
September and April present distinct weather contrasts, reflecting the transition between summer and autumn versus the approach of spring. In September, temperatures range from a minimum of 9°C (48°F) to a maximum of 31°C (88°F), with an average of 22°C (71°F), indicating warmer conditions. September also experiences higher precipitation, totaling 136 mm (5.4 in) over approximately 9 days, coupled with a humidity level of 77%. In contrast, April features cooler temperatures, with a minimum of -1°C (30°F) and a maximum of 28°C (82°F), averaging just 12°C (54°F). Precipitation is significantly lower in April at 54 mm (2.1 in) across about 5 days, and humidity is slightly lower at 75%. For a more detailed look at the weather patterns in April, visit Osan weather in April.
September and May both showcase a range of warm temperatures, but September tends to be slightly warmer overall. In September, the minimum temperature is 9°C (48°F) and the average reaches 22°C (71°F), climbing to a maximum of 31°C (88°F). In contrast, May starts off cooler, with a minimum of 6°C (42°F) and an average of 18°C (64°F), also peaking at 31°C (89°F). When it comes to precipitation, September experiences more rainfall, with 136 mm (5.4 in) over 9 days, compared to May's 98 mm (3.9 in) over 8 days. Humidity in both months is relatively high, with September at 77% and May slightly higher at 81%. For a more detailed look at May weather, you can check Osan weather in May.
When comparing the weather in September and June, both months present mild average temperatures, hovering around 22°C (72°F). However, September features a broader temperature range with minimums dipping to 9°C (48°F) and maximums reaching up to 31°C (88°F), while June tends to be slightly warmer overall, with a minimum of 12°C (53°F) and a maximum of 33°C (91°F). Additionally, September experiences more precipitation, totaling 136 mm (5.4 in) over 9 days compared to June's 80 mm (3.1 in) over 7 days. Notably, humidity levels are a bit higher in June at 85%, compared to 77% in September, contributing to the warmer feel of early summer. For a closer look at the specifics, check out Osan weather in June.
In comparing the weather between September and July, we see distinct differences in temperature and precipitation patterns. September experiences milder temperatures, ranging from a minimum of 9°C (48°F) to a maximum of 31°C (88°F), with an average of 22°C (71°F). In contrast, July is significantly warmer, with temperatures ranging from a minimum of 18°C (65°F) to a peak of 36°C (98°F), averaging 26°C (79°F). Additionally, July sees more rainfall, with 235 mm (9.3 in) over 14 days, compared to September's 136 mm (5.4 in) across 9 days. The humidity is also higher in July at 91%, compared to 77% in September. For more detailed information about July weather, visit Osan weather in July.
September experiences a noticeable shift in weather compared to August. Temperatures drop significantly, with September's minimum at 9°C (48°F) compared to August's much warmer minimum of 16°C (61°F). The average temperature in September is 22°C (71°F), while August boasts a higher average of 27°C (80°F). Additionally, September sees a maximum temperature of 31°C (88°F), which is markedly lower than August's peak of 38°C (101°F). Precipitation also decreases in September, with 136 mm (5.4 in) falling over 9 days, compared to August's 255 mm (10.1 in) over 14 days. Humidity is slightly lower in September at 77%, compared to August's 91%. For a more detailed look at conditions during the hottest month, you can check Osan weather in August.
In September, the weather is notably warmer, with average temperatures reaching around 22°C (71°F) and maximum highs climbing to 31°C (88°F). The month sees a higher rainfall of 136 mm (5.4 in) over 9 days, contributing to a humidity level of 77%. In contrast, October ushers in cooler temperatures, with an average of 15°C (59°F) and weekend highs of 29°C (84°F). Precipitation decreases significantly to 62 mm (2.5 in) over just 5 days, while humidity edges slightly higher to 79%. For a more detailed overview, check out Osan weather in October.
September weather is generally warm and pleasant, with average temperatures around 22°C (71°F) and maximums reaching up to 31°C (88°F). The month sees a fair amount of rainfall, totaling 136 mm (5.4 in) over about 9 days, coupled with a humidity level of 77%. In contrast, November brings a noticeable drop in temperatures, with averages around 8°C (46°F) and nighttime lows plunging to -5°C (23°F). Precipitation decreases significantly to 54 mm (2.1 in), falling over just 5 days, while humidity remains slightly higher at 80%. For a detailed look at November weather conditions, you can visit Osan weather in November.
September and December present stark contrasts in weather. In September, temperatures range from a mild minimum of 9°C (48°F) to a warm maximum of 31°C (88°F), with an average of 22°C (71°F). The month experiences significant precipitation, totaling 136 mm (5.4 in) over 9 days, accompanied by a high humidity level of 77%. Conversely, December brings much colder conditions, with temperatures plunging to a minimum of -14°C (8°F) and peaking at a maximum of 13°C (56°F), averaging just around 0°C (33°F). Precipitation drops significantly to 26 mm (1.0 in) over only 5 days, and humidity decreases slightly to 74%. For more details on December weather, you can check Osan weather in December.
As summer transitions into fall, September in Osan welcomes milder temperatures and a refreshing change in climate. With an average of 22°C (71°F) and a comfortable humidity level of 77%, this month offers a pleasant respite from the peaks of summer heat. The chance of rain, with 9 days of precipitation totaling 136 mm (5.4 in), adds a touch of renewal to the landscape. This contrasts sharply with the scorching summer temperatures, making September an ideal time for outdoor activities and exploring the beauty of Osan. For more detailed insights on what to expect throughout the year, check out Osan Climate.