Weather will likely play an important role when you plan your trip to Onamia, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually July and August, with an average temperature of 19°C, while the coldest months are January and February, with an average of -8°C. The snowiest months in Onamia are March, April, January and December, with each month seeing an average of 19 cm of snowfall.