The climate in Macedonia is quite diverse. In most of Macedonia the summers are long and hot, and the winters mild and wet. Totally different climate is in the mountains. Winters can be long and full of snow. Summers can be chilly there.
Especially the climate in Ohrid is very pleasant. Nice warm summer days and cool summer evenings. If you can't stand the heat, the best months to travel are May or September. The temperature is then pleasantly warm and it is not very crowded.