An unexpected spring freeze, whether in the form of frost or rain, can put a dent in gardening plans. It is important to protect your plants from freezing rain in order for them to be healthy and flourish the rest of the spring and summer.
Water the plants during the hottest part of the day when freezing rain is predicted. This will seep into the roots, and once the cold rain hits the area around the plant's soil, the moisture will rise up to heat the plant. This will also help insulate plants that are going to be covered with blankets or tarps, as the water in the soil will produce heat under the tent, warming the plant.
Layer some shredded bark or straw around the base of the plant before expected freezing rain, which insulate the roots.
Cover climbing vines or trellis plants with blankets, an old shower curtain or tarp, or sheets of canvas. Pin or nail the material to the wall on either side of the vines, covering them completely. Pin the top of it as well so the rain cannot seep down under the top of the material. For plants on a trellis, drape the material over the trellis and tuck it under around the bottom of the structure. Have these materials ready so you can install them as soon as a cold rain begins to fall.
Cover young plants such as vegetable, fruit or herb gardens with an old shower curtain or tarp (just make sure it is waterproof). Tuck the material down under and around the plants.