If you want to have real fun with snow, and real means something extraordinary, go for Roopkund Trek during  May. The roopkund trek will give you some real thrills with snow.

If you want to trek on snow and see some of the precious high altitutde water fall  then go for Rupin pass  trek.

I did both trek  i think rupin pass trek is better trek in the month of may or june,
Rupin pass has all the surprises packages for its trekkers who come to explore nature in its most pure form.

• Right from sunrise and sunsets
•  snow beds of the crystal clear snow to waterfall views
• hanging village. The village is actually hanging off the cliff
•  view of Kinner Kailash
•  snow bridges
• Lush forest
• and highly visited Kennaur temple.

Roopkund Trek Highlights

• Explore the mystery of the Skeleton Lake, Roopkund, witness the years long buried human  bones in the snow
• Enjoy the breathtaking views of lofty Himalayan peaks like Nanda Ghunti & Trishul
• Cherish the sprawling lush meadows of Bedni and Ali
• Get an opportunity to visit some of the remotest villages of Uttrakhand (lohajung, Didina and Wan Village)
• Enjoy the opportunity to camp under the open sky and amidst the stunning landscape