All outdoor plants will need to be covered the next three nights in the Phoenix Metro area. With lows forecasted in the 20’s, this will definitely harm landscape plants as well as your gardens. It will be windy too so be sure to secure the frost cover with something so it doesn’t blow away. I used large river rocks, pots without plants and even binder clips!
If you can bring potted plants onto a covered porch or patio, next to the house, that will help protect them. Protect the citrus trees with old-style Christmas lights (a little heat) and then a cover. Works for the other plants as well.
Remember, the frost cloth needs to drape all the way to the ground to be most effective. And put them on just before sundown to keep the heat from the sun that is in the soil.
Here's a few good articles on protecting plants from frost:
Wishing you and your plants well!
The Garden Goddess