Strawberry, many nursery growers use raised benches...since hot air rises you actually would be moving the plants to a slightly warmer environment. What quantity of plants are you needing to raise? You can put a string of low wattage lights under the plants to add some bottom heat; or youcould "box in" the sides of the raised bench to minize air circuloation underneath.

strawberry,
Another way might be this. (Of course if you have huge pots or too many it would be too much labor)

Double pot them by getting a larger pot than the original one, put dirt in the bottom--- set the original pot in and then fill in with dirt between the larger pot and the one with your plant in it.

I used to do that when I had a bazillion small clay pots with boxwood plants in them to keep watered during hot weather. (Not mine--- the owner of the ranch we were caretaking )---
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It kept them from drying out when it was hot and it might also work to protect the root system in the cold. Sorta like a thermos bottle.

cave76