If you mean temperatures will fall to 30-31 degrees Fahrenheit then yes there is a risk, not great but possible.
Try covering your plants with horticultural fleece or old newspaper.That should provide sufficient protection.

Boss....yes I see in the paper where temps are falling in the south....Tampa/St Pete is welcoming snowbirds with 50 degree for daytime.

Your new plants could be touched by cold ovrnight so the easiest thing to do is....if they are in pots, just take them to your garage or shed...or someplace out of the cold for nighttime and put them back into the sunshine during daylight hours.

If they are in the ground, then as Mel says, cover them with a sheet held up away from the plant...cover them completely with a bushel basket or picnic hamper. Your garbage can might be employed...a plastic garbage bag held away from the plant by means of stakes put into the ground around the plant....but be sure to remove any such covering before the sun rises.

In the fall, geraniums in their soil can put up with temperatures as low as 25 F.....but why take the chance if protection can be given.