High Tunnel Gets Colder Than Outside

[Cole_Robbie]

That graph tells the story. The full article about it is here:
http://www.hort.cornell.edu/hightunn...isons_reid.pdf

http://www.hort.cornell.edu/hightunn...stic_study.pdf

I'm still struggling to grasp the physics behind it, but on clear nights atmospheric radiation can make a high tunnel drop below the outside temperature.

I thought this idea was worthy of a thread, for everyone growing under plastic. Whether you have a high tunnel, or just a few shelves with a drop cloth over them, it's quite possible for your plants to freeze even when the outside temperature never gets to freezing.