Planting early means we must have everything ready to cover and remove cover often.
We will dip down to a freeze tonight so everything has been put to bed.
Now it is daylight and the sun is up. This is very important!!
Check on the inside temperatures often! Once the sun is fully on the plastic I open one end so the plants do not scald. A few years ago we learned the hard way that plants will burn easily when the sun heats up the inside dome. In our greenhouse the outside temperatures were very cold and the inside temperatures got very hot from the sun.
I just opened this side and in a hour I will probably open the other end so the air will flow through. I will close the ends when the sun goes back down later today. It takes a bit of work but worth an early harvest. Onions and cabbage are cold weather crops but a freeze on this type of cabbage I don't want to risk since they are so young.
The greens like lettuce and spinach, turnips etc need more protection from cold. But the main thing here is open up your plastic shelter when the sun comes up if you are just slightly below freezing because it can get hot inside when the sun hits the plastic. I don't know anything about a deep freeze because I have never planted vegetables when it gets into the teens or below.