NOTE: I know very little about growing starter plants from seed indoors; I know absolutely nothing about growing them in a cold frame, so I apologize if my questions seem dumb.

The things being grown in the cold frame will be starter plants, and they'll be veggies; I know some veggies can grow fine in an unheated cold frame (any cold weather veggie.....cabbage, broccoli, lettuce, etc.)

I know on a sunny day the inside of a cold frame can get quite warm and will need to be opened a little bit for ventilation.

I plan on growing winter squash, cucumbers, melons, and some herbs (sage, basil, rosemary, chives) in the cold frame.

Since I know melons, cucumbers, and melons LOVE heat, would the cold frame have to be heated, or would they do alright in an unheated cold frame during the day or would it have to be heated? What about the herb varieties I mentioned? Would they do okay in an unheated cold frame?

Right now it's in the 50's and 60's during the day; I can germinate them indoors using a heat mat for faster germination but they'll be grown as starter plants in the cold frame.

I am going to assume that due to where I'm located (northern Michigan) I would have to heat the cold frame at night?