I have some family south and west of Minneapolis. I don't believe they do much gardening until after May 15. Steve S

Yea, I am not really planning on getting them in the ground until the 15th - unless we continue to have a really warm spring (I've already got waist high clematis, blooms on my trolius, the lilacs around here are blooming...).
My question related more to whether or not having them in the fridge was ok if they have sprouts AND exactly how people take the ground temps.

Hey there,

The refrigerator might be a little too cold.

Instead of 60 degrees, you could just plant them when everyone usually plants their tomatoes or melons. Melons are usually a couple of weeks later.

I am not sure about that 60 degree figure and think it might be folklore. Please see other messages on the forum, where other people also discuss, including someone who is experimenting by planting out tubers early in zone 5. If you do want to go with 60 degrees, it refers to the AVERAGE through the day and night, and I think also refers to 6 inches down, where people usually plant their tubers.

If I were you, I would start the plants inside in pots and then bring them out in a few weeks. You could also keep them outside during the day when temperature is high enough. Mine thrive this way.