It depends on where you are. In SE where I am, I often ride at least one day a week all year. It was possible to do that for the past three years in Sitka. This last winter we had maybe 7 -10 nights of freezing weather was all.
In Anchorage where my boy lives he was out in March this year, but that was early. He's usually servicing his Jackal about now. He'll ride till October.
Other places have other seasonal norms. All Alaska riding seasons unofficially happen after 'breakup' when the surface snow melts and the river ice breaks up. Up until then ice and temperatures are factors. During breakup the roads are horrible -- muddy, sunken, potholed, flooded, etc. But a soon as it settles down it's getting toward midnight sun time and the riding days are long. They can be hot, too. I've been up at the artic circle when it was full daylight at 1AM and 95ºf. And of course the bugs are epic.