Following on AKsilvereagle's suggestion regarding the Cassiar, it is another reason to take the AK Hwy northward in the spring and Cassiar south later in the summer or fall.
The AK Hwy is better maintained through the winter and usually needs less spring tweaking. The infrastructure is also more robust.
The Cassiar is more prone to flooding and washouts in the spring due to the spring melt from the mountains. The Cassiar route also gets a heavier snow load through the winter due to it being more "coastal". The freeze/thaw cycle also creates more potholes and pavement breaks that need repair. It takes the crews a while to cleanup the route in the spring. August and September are a better time to travel the Cassiar if you wish to have the best conditions.
Having said that, both the Alaska Highway and Cassiar Highway experienced washouts a couple of years ago in the spring. On the AK Hwy, a bridge washed out at Rancheria YT; crews had traffic moving again in four days. On the Cassiar, the road simply went underwater in a marshy area.
There's another troublesome spot on the Cassiar that has held us up on two separate trips; a creek usually overflows its channel and sweeps across the road. On one trip, we were piloted through the area with the water still running across the highway.