Taking the local weather in Ona into account is an important factor for planning your visit, especially if you plan to spend your trip by the pool. The hottest months are usually August and July, with an average temperature of 13°C, while the coldest months are February and January, with an average of 3°C. The rainiest months in Ona are September, October, December and August, with each month seeing an average of 214 mm of rainfall.