What to do about mild overnight freeze

Denver in October. Usually, nights are in the 40s F. But just tonight (actually early tomorrow morning) the temperature dips below freezing, then goes right back to 40s at night. Also, there may be some rain off and on tonight and maybe tomorrow morning.

I have stuff that I would like to leave a little longer: sweet potatoes, butternut squash. I would like to leave tomatoes a little longer, I doubt that can happen.

If it wasn't for the rain, I would throw my old towels and t-shirts over the plants. But having them wet from rain might make it worse.

Any ideas?

Update: after checking weather again, I don't think there will be rain. I guess I will try covering with the old t-shirts and towels. Unless I shouldn't.

If you had some water proof options like a tarp or plastic of somekind I would probably use that if there was rain called for. Otherwise, yes, like you said old t-shirts, towels, sheets, etc are generally good enough to keep frost off the plants for a small freeze like you are describing.

On a different note, I recall reading in the book "Farmer Boy" where they were out in the middle of the night pouring water over the plants before sunrise. There was something about the frost plus sunlight. Not sure how much of that was story and how much was science, but it is an interesting anecdote.

How many plants and how big an area?

If its just a few, sheets and towels are great. Big areas need the large row covers made for this application.

Frost works by radiating heat into cold outer space on clear nights. It worse at higher elevation (like CO), still air, and low humidity (also CO). Air temps below freezing are obviously a problem - blankets and row covers block air flow.

So we counter it by blocking the radiation to space and blocking cold air movement. Multiple layers are better than one. Quilts and thicker blankets are better, because the top side can get colder while the inner layer stays warm. The ground and the plants are radiating heat up the blanket. So do everything you can to increase the heat storage, conductivity and emissivity of the ground and plants...

- You might try removing light, fluffy, dry mulch from under the plants - this blocks the heat from the ground.
- Water thoroughly - moist soil conducts heat much better than dry, and the heat capacity of the water adds to your energy reserve. Wet foliage is bad for mold and fungus, but adds a slight measure of protection from frost - the plants can't freeze until the liquid water freezes first.
- Old milk jugs or buckets of warm water next to the plants, under the cloth covers, will release heat and keep the important parts above freezing.
- Suspend the blankets above the plants so there is a gap, otherwise the parts of the plants touching the blanket will get colder faster.
- Make sure the space between the warm moist soil and the plants is open so heat can convect and radiate up to the plants.

Hope that helps, but its a lot to get done this afternoon before the dark and cold arrive!