What is the best season to view waterfalls in Switzerland? I'm thinking spring, once winter ice and snow begins to melt.
Early summer, because you may not be able to get close to them in spring, depending on trail conditions. Also, your visit is more likely to coincide with sunny weather in the summer. Spring is generally not a great time to visit the Alps, unless you're there early in the season for skiing.
Mid to late June, for me. Warm, sunny (mostly), dry (mostly), and plenty of flow in the falls. We were there just a few weeks ago and Giessbach, Reichenbach, and Staubach Falls were all doing fairly well at the start of September. Not as well as they would have been in early summer or late spring but still fun.
Spring or early summer, March to June. This is when the winter snows are melting and there is the maximum water flow, After that the flow decreases in the summer. Once the snows start again in the High Alps (October onwards), it decreases again as all the snow is staying up in the Alps, until the following spring when it melts again.