Hello jim,

Seems to me the southern route would be preferred in April--not overwhelmingly hot then, but you might find a tornado or two (or dozens of storm chasers on the highways). Your subject to some late-season snow in ND and MT come April. Not that it would be expected to be a real problem, but it could slow you down. I would not enjoy visiting NM, TX, OK, etc in June, either, as it's gotten seriously hot by then. Running hard and running the A/C in your car hard can combine for a difficult trip for your wheels.

If it's June when you go, I'd go north. By June, ND, southeast MT, and northeast WY and all of SD are about as green as they're going to get. You'll have opportunities to see the Northern Lights on Michigan's UP, and it's VERY nice and remote all the way from the big bridge at Mackinac Straits to the WI line. Plus, the farther north you go, the longer the days as you approach the Summer Solstice in the 3rd week of June, perhaps an advantage on a speed run.

If a "touch and go" is all you need to bag a state, be aware that US 2 dips into WI at Florence just west of Iron Mountain, MI and of course you have part of WI to traverse at the western end of the UP, too, between Hurley and Superior, WI, so routing back into WI enroute to Chicago isn't necessary unless you just prefer to do so.

Have fun with the planning!

Foy