Though the Chopta to Tunganath trek is open for most times of the year, however my suggestion would be to take this during the months of March Mayor the months of September October. The weather during these months are better and is suallly not known to have much rains. Though we did have a rainfall , but that was got a half hour or so and it painted a rainbow for us on the snow covered peaks.
Reaching Tunganath :
Our last rest was about a km away from Tunganath at the last wayside tea-stall. The trek gave us majestic sight of the peaks of Panchchuli, Kedarnath , Nanda Devi, Nilkanth mountain peaks on a clear sunny day .Hands were feeling numb, faces were taught with the chill and noses were getting moist and running by then. I was getting out of breath every couple of minutes, and had to take a breather at every corner and turn. At about 10am we finally reached the holy site of Tunganath.