There are several things you can do about this, and depends on your situation.

1. Cover them with cloches. You can use cut off milk cartons or any container. Even cardboard boxes work. You can leave the lid off containers for air. Just remember to remove them in morning so plants don't cook in the sun.

2. Row cover cloth. Cover the plants with this. This only works for very mild frosts.

3. Spray with fine water mist. Believe it or not spraying with fine water will cause the water to freeze and release heat, preventing the plant from freezing. Used by many farmers, including citrus growers.

4. Build fires. Not sure you want stay up to maintain fires, or even build one where you live, but this is another farmer's trick often used to protect grapes. The radiant heat from a fire keeps plants from freezing. This also moves air which can also help as still air causes the worst damage.

Damage can be variable from a few dead leaves and/or stems to loss of fruit set, to death of the plant. You'll have to assess any damage after the freeze. Good luck!

I bought a couple of Husky Cherry Reds at WM a few weeks ago, tempted by our own warm March to hope for some ripe fruit before I can expect any from my still-in-the-basement seedlings (which will be late, as usual). We had lower temps than predicted one night last week, and one of the plants has a 1" white spot on a top leaf.

Your plants are probably too large for OJ cartons or 2-liter bottles, but Capoman's suggestions will work, also old sheets or any spare fabric, up-ended buckets or trash containers, etc. You don't want to risk the temps being a little lower than normal and reducing your plants to stumps....

We're supposed to have lows of 36, 30, and 36 the next three nights. My tomato was damaged on a night when the low was supposed to be 36, so I'll be protecting them starting tonight.

Agree with missingtheobvious. Take whatever steps you need in your situation even when temperatures within a few degrees of frost are forecast. Remote thermometers with alarms can be handy if you are willing to get up in the middle of the night to save plants. These are the risks of planting out early. Set them a few degrees above freezing to give you a bit of a buffer to work with.