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Osan Weather by Month
Average temperatures, rainfall and humidity for Osan, Korea, South, month by month, built from OpenWeather's historical records. Use it to see what a typical Osan month looks like before you travel — then check the live Osan forecast for the days ahead.
Warmest month
August
31°C average high
Coolest month
January
-8°C average low
Wettest month
July
131 mm of rain
Driest month
January
11 mm of rain
Average temperature and rainfall in Osan by month
Averages of the daily highs and lows recorded in each month, with total rainfall, mean humidity and mean wind speed.
| Month | Avg high | Avg low | Record low / high | Rainfall | Humidity | Wind |
|---|---|---|---|---|---|---|
| January | 3°C | -8°C | -21°C / 15°C | 11 mm | 68% | 8 km/h |
| February | 6°C | -5°C | -18°C / 19°C | 21 mm | 66% | 9 km/h |
| March | 13°C | 1°C | -9°C / 28°C | 32 mm | 63% | 9 km/h |
| April | 19°C | 7°C | -2°C / 31°C | 48 mm | 63% | 9 km/h |
| May | 24°C | 13°C | 4°C / 33°C | 42 mm | 68% | 9 km/h |
| June | 28°C | 18°C | 11°C / 35°C | 48 mm | 72% | 8 km/h |
| July | 30°C | 23°C | 16°C / 38°C | 131 mm | 80% | 8 km/h |
| August | 31°C | 23°C | 14°C / 38°C | 99 mm | 79% | 7 km/h |
| September | 27°C | 18°C | 8°C / 36°C | 65 mm | 77% | 7 km/h |
| October | 20°C | 9°C | -3°C / 29°C | 45 mm | 75% | 7 km/h |
| November | 12°C | 2°C | -9°C / 28°C | 35 mm | 73% | 8 km/h |
| December | 4°C | -6°C | -19°C / 19°C | 21 mm | 71% | 7 km/h |
Best time to visit Osan
The most comfortable time to visit Osan is generally May and September to October, balancing mild daytime temperatures against the driest stretch of the year. The city has strongly marked seasons and rain concentrates around July, totalling about 597 mm a year.
Travellers who prefer heat should aim for August, when highs average 31°C. July is the month to avoid if rain would spoil your plans — it averages 131 mm, roughly 12× the rainfall of January.
Source: OpenWeather historical and statistical weather data. Values are long-term averages, not a forecast — see the Osan forecast for what is happening now.