Jared - your temps are well within the tolerance of most orchids just keep doing what you have been and you will be fine, remember that the plants will tolerate the cooler temps if kept on the dry side, it won't hurt them to go for 10 plus days without water. Keep us posted on how you are making out.
You could place a large open container of water in with them. The humidity it creates will generate some warmth. If you could heat the water, even better. If you have a flashlight, the bulb could give off some heat if you are afraid night temps will get really low. Turn it on and leave it in your tent...just be careful your fabric won't overheat by touching the bulb.
Good luck! I imagine they are hardier than we think.
Hey all...I'm happy to let everyone know my power is back and all my orchids survived! The temps in the shelter tent never got below 59 degrees...I did not even have any drop buds. Great news as I was pretty concerned the night that the temps went down to the teens!!!
Anyway, thanks to everyone who posted comments/advice!
I think if the blankets you are using are keeping them at a min of 59F then you should be fine. Mine go down to that on a normal winter night because I have the thermostat set to 59F during the night to save energy.
Phals go dormant but survive fine, Oncs don't seem to notice, nor do Dens or Paphs.
When I read 20F I was worried, but if you can keep them closer to 60F or only a fraction below then you should be fine.