There are only two seasons in Zanskar (October to May) - Winter and Summers (June to September). To plan a holiday in Zanskar for sightseeing, July to September will be the best time. And for trekkers, winter will be also a good time as this is when one get to enjoy the famous Chadar trek and Padum Trek. During the winters the temperature may get as low as (-15°C) but the views like frozen waterfall and river that one get to see are just soo beautiful. See below for all the details
Summer starting from May is the best to experience the rustic beauty of Zanskar Valley. The weather is neither too hot nor too cold just the perfect to enjoy the rustic beauty of the place. Also this is when one gets to enjoy the famous monastery festival of Zanskar.
During the winters it's get way too cold. The snow falls, the river freezes and tha place becomes just the perfect playground for the trekkers. Many of the treks in Zanskar are counted amongst the best winter treks in India.