A Gardener's Guide to Frost

/Home/Garden Basics/Plant & Lawn Care/Garden Problems and Solutions/Garden Frost

by Farmers' Almanac Staff | Monday, September 22nd, 2008 | From: Home and Garden

Clear or Cloudy Sky?
Frost (also called white or hoarfrost) occurs when air temperatures dip below 32°F and ice crystals form on plant leaves, injuring, and sometimes killing, tender plants. Clear, calm skies and falling afternoon temperatures are usually the perfect conditions for frost. If the temperatures are falling fast under clear, windy skies-especially when the wind is out of the northwest-it may indicate the approach of a mass of polar air and a hard freeze. A hard or killing frost is based on movements of large, cold air masses. The result is below-freezing temperatures that generally kill all but the most cold-tolerant plants.

Cloudy Skies: you may be in luck.
If the temperature is cool, but clouds are visible, your plants may be protected. During the day, the sun’s radiant heat warms the earth. After the sun sets, the heat radiates upward, which lowers the temperatures at or near the ground. However, if the night sky has clouds, these clouds will trap the heat and keep the warmer temperatures lower, closer to your plants, preventing a frost.

Copyright ©2012 Almanac Publishing Co. All rights reserved.