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.
Gas cost estimates for this Salt Lake City to Boulder trip. If you were travelling in a vehicle that averaged 35 MPG and were paying $3.54 per gallon for your gas then the cost for a trip based upon an estimated distance of 424.8 drive miles from Salt Lake City to Boulder * in gas would be in the region of $42.97 USD.