This is April (even late April) in Wisconsin. I awoke on Monday to find an inch already on the ground. It snowed all day.
These are the same cold frames completed on a beautiful Sunday afternoon. I hammered 4 boards together in a box and stapled vinyl (the kind you find in Walmart's fabric department on a large roll) over one side. I also planted out my spinach (already throwing off pollen), lettuce, white mustard, and a few broccoli plants.