Weather will likely play an important role when you plan your trip to Asan, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually August and July, with an average temperature of 23°C, while the coldest months are January and December, with an average of 1°C. The rainiest months in Asan are July, August, September and June, with each month seeing an average of 222 mm of rainfall.