The weather forecasts predict lows in the 20’s coming up. With the unusually warm weather we have had, plants are more tender and subject to cold damage than they would be in a normal winter. Flowers are likely to freeze, especially on trees like magnolias, which are the plant poster children for freeze damage. There isn’t much you can do to protect flowering trees.
You can protect flowers on pansies and perennials, and recently planted shrubs—plants that are close to the ground–by placing a blanket over them for the night. The idea is to hold warmth from the soil (the ground is pretty warm) and also to reduce what is called radiation heat loss to a clear sky. The latter is usually more of a problem on the second night of cold weather, when the wind velocity drops (wind mixes warmer air from near the ground with colder air at plant level) and the sky is clear.
A blanket or newspaper are good insulation; plastic sheeting or a tarp are not; you might put down a layer of newspaper and hold it in place with a tarp. The protection can stay on during the day Saturday, but should be removed Sunday and if the forecast is accurate, you should not need to protect plants on Sunday night. Remember that anything heavy is likely to damage open flowers, but it’s safer than no cover at all. As far as what I am going to do…probably nothing, since I haven’t planted anything yet this year. But if I had just planted a budded or blooming pieris or a forsythia, or a hydrangea with leaves showing, I would wrap it in a sheet or light blanket.