Clouds will help to insulate and slow the loss of the heat, but a cloudless, wind free night will afford no protection whatsoever. The temperature within the soil and in the plant's cells may even drop to a few degrees colder than the air. As the temperature drops, the moisture in the air condenses into dew, which then freezes when the temperature reaches 32 degrees F. on the plant surfaces. At 32 degrees, damage to most plants may be minimal, and only affect a leaf or two. However, if the temperature drops far enough for the plant cells to freeze, non hardy plants will die.
Weather conditions can bring about a frost, even in supposedly frost free areas.
It is important to heed the warning when your local forecaster announces 'a chance of frost', and take precautions to protect your garden. Helping your garden survive a frost The best way to avoid frost damage to your plants is to grow plants that can withstand the frost. It is a good idea to ask a qualified local nurseryman what is suitable to grow in your area. Even better, look around your own neighborhood, and see what survives and thrives in other gardens. Plant varieties of plants which flower late, in areas where late spring frosts may occur.