I visited Bryce and Zion in late October.
Nights were cold but usually warmed up to the 70s by mid morning.
If you have your heart set on it, bring long johns and a sweater.
You may wish to stray into eastern Wyoming and South Dakota on the way out or the way back.
There is Devil's Tower, Sturgis, Deadwood and Mt. Rushmore all in the same area,
Don't forget Badlands national park.
He is based in Vancouver Island afaik,