While early June is often the best time for riding the Haul Road/Dalton Highway, a little later provides better sightseeing due to vegetation having time to flourish under the northern sun. Things can look pretty gray and gloomy until trees are in full foliage. This happens by early June at lower elevations, but takes a few weeks longer in the passes. While I have run into snow at Summit on the Alcan in late June, I have also had no trouble riding south in early April - although riding at 15 below F was a mite uncomfortable. On a ride back north in '03 the only snow I hit was going over Steamboat on May 16th. This was Muncho Lake on May 16, 2003 - Snow falling on the far hills, but none made it to the highway. Lakes up north thaw out a little later than down south. Here's Kluane Lake almost ice-free on June 8th, 2002 - Muncho Lake again on May 10, 2002 (Yes, that's solid ice) - But once north of the Rockies it can also be quite warm around Whitehorse and on up through the Tanana River valley to Fairbanks. It's best to be prepared for a wide variety of weather, any time of year.