Yes, May is a good time to visit Rishikesh. It is the ideal time for adventure activities as well. Some of the activities that you may enjoy are – river rafting, ziplining, bungee jumping, giant swing, cliff jumping etc. You can watch this video to see the things that you can enjoy in Rishikesh: https://www.facebook.com/Tripoto/videos/1426330960786618/
I think May is not good time to visit Rishikesh. Rishikesh Adventures is also famous as Sports Capital. Rishikesh is a popular place in India for backpacking and adventure sports such as bungee jumping, mountain biking, rock climbing and rafting.
The best time to visit Rishikesh is between October to March and between April and September. From the month of May there starts a lot of heat. Travelers are advised not to come here in the month of May as the weather here is very distressing during this time. In Rishikesh, the month of monsoon starts from August to July. At this time rafting is also stopped.
Yes, you can experience the thrill of River Rafting and Bungee Jumping in the month of may, and you can also enjoy other adventure activities like Body Surfing, Jungle Walk, Cliff Climbing ,Trekking and many more.