What is the best time to go tour the Grand Canyon with temperatures under 80 degrees?

I visited in December and just missed a snowfall. I would concur with the answers already provided.

Now

Feb to March is the best time with temperatures under 80 degrees...

It depends on if you are planning on just touring the rim areas or planning an involved hike down to the river. It is lovely right now. Medium to light jackets on the rim.