Yup, I've got snow on the ground too. The trays of broccoli, thyme, onion, parsley are back in the house. There are seeds in the ground, lettuce, swiss chard, spinach. They will be fine. It's all cold hardy stuff, I'm not worried. Probably the plants would have survived if left out, they've been out enough now, but the onions are mostly still so thin and spindly I decided not to stress them. I haven't grown kohlrabi myself, but I think it is very cold hardy and should be fine. This time of year it gets cold, but it doesn't stay cold real long.