Marginal Weather Tire Advice Wanted

[dbear61]

I have planned a massive road trip to begin three weeks from today (departure 5/23). Milwaukee to Seattle via ND and MT. The return will bring me to Yellowstone for three days starting 5/30 and then to the Black Hills on 6/4 for another three days with hotels reserved all along the way.

My worry is with this wretchedly cold Spring, and the snow that continues to pound the high altitudes in the West, can I still get by with Summer Sport Hankooks, or should I sink $500-$600 insurance into an all-season set of tires that I would only use for this trip?

Based on how this Spring has gone, I'm expecting temperatures in the 20s, maybe low 30s, for morning starts, and possibilities of snowfall?

It's got the PSM option, so I would like to think careful driving could get me through even coldest temps (but probably not snow), but I have no experience to support that hope.

DBear