Doing your shakedown tour locally makes more sense. Northern WI and MN can be pretty damn cold at night, even in the summer. I've seen about 30F lows in the Boundary waters before. In August. More than once. Not on the same trip. Locals swear it's unusual, but... In my opinion, the locals have had their brains frozen a few times too many . (I'm hoping that for once I get to see it trying to be hot in the Boundary Waters, but I'm not holding my breath...)

Things will be warmer near Lake Superior or Lake Michigan, but if it's a cold summer, not all *that* much warmer. And unfortunately, a cold summer does not dissuade the fearsome state bird. You will want DEET.

San Francisco winter conditions are probably decent prep for a cold summer up here. A cold LA winter is definitely comparable. LA will have more rain, and perhaps slightly sharper temperature swings, but otherwise is very like. (desert in rainy season vs giant bog in dry season)