What are the best months to vist the National parks out in the western USA? And why?|199508

We would like to see Yellowstone, Yosemite, the Painted Dessert, Grand Canyon, Zion, and Bryce, Grand Teton.
How much time will we need?

Spring (April, May or early June) or Fall (September, October). Summer is entirely too hot and Winter is rainy and cold.

And you_re going to need a lot of time. 4-6 weeks for a thorough visit to each one.

umm around early spring because its not too hot and well the wildlife is more active after the harsh winter