The best time to visit Manali is either between April to June or September to October. In summers you can enjoy rock climbing and river rafting along with a lot of excursions, whereas during winters you can play in the snow and enjoy skiing on the slopes.
In winters, the temperature can drop below freezing point when heavy woolens are required. Summer temperatures are mild and light woolens/cottons are recommended. In Manali, one can find high mountains shrouded by silent snows and deep boulder strewn gorges. There are thick forests, filled with cool breezes and bird song.