From Toronto in mid September to Quebec City in late September, hypothetically you really could encounter everything from shorts-and-sunscreen weather to boots-and-jacket weather.
The driving distance between Denver, CO and Salt Lake City, UT is 536 miles. The driving time would be approximately 8 hours 30 minutes if driving non-stop in good conditions.
Travel thoughts for your from Salt Lake City to Boulder. Driving By Car: If you were in a car and maintained an average speed of 60mph (96 kmh) over the course of your it would take you around 7.2 hours to get from Salt Lake City to Boulder.