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.
1 I-25 (north and south), I-70 (east and west), and I-76 (northeast) are the major interstates leading in and out of the city. I-225 and I-270 cross the Denver area.  U.S. Highway 40 connects Denver to Salt Lake City to the west.