JACKSONVILLE, Fla. – It’s that time of year where frost is a concern for parts of the region. But how does frost actually form? And what should you do protect your plants and vegetation?
Let’s start with frost formation.
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Forming frost
There are actually two metrics meteorologists use to help decode the atmosphere. You’ve probably heard of the air temperature, the one that is actual temperature outside.
But meteorologists also use a measurement called the dew point to measure how much moisture is in the atmosphere. The difference between the air temperature and the dewpoint is how relative humidity is measured.
When the air temperature and the dew point is exactly the same, the atmosphere is fully saturated. The result is humidity of 100%. The saturation of air is the first step toward frost.
The ingredients necessary
Often, the air temperature falls back toward the lower dewpoint during the overnight hours as the atmosphere cools. When this happens during warmer weather, the result is dew developing on outside surfaces. This is often seen on grass, vehicles, and trees.
When the dew develops in cooler weather, it can freeze. The frozen dew is known as frost.
Meteorologists begin looking for conditions for frost when lows are forecast to fall into the mid 30s, there is decent moisture content in the air, and winds are forecast to be calm.
Frozen ground above 32°?
Frost often occurs when morning lows are in the mid 30s.
So how can something be frozen when it’s not below freezing?
Air temperatures are normally measured at around 6 feet. But it is often cooler just a few feet below right at the surface.
So a morning low of 35° often means an actual ground temperature below 32°, which allows frost to develop.
The intensity of the frost (patchy to widespread) is often a product of how much wind is in the area, and how long temperatures right at the surface stay below freezing.
Protecting your plants
With frost in the forecast, there are some steps you can do to protect your plants and sensitive vegetation.
First, if possible, potted plants need to be brought indoors. These plants are often the most susceptible to frost damage.
If the plant is too large, a sheltered location like a garage or up against a shed or house will help prevent frost.
Sensitive vegetation will need to be covered to prevent frost damage. Natural fabrics like burlap are preferred, but plastics like tarps can also be used.
Sensitive plants like rose bushes will also need to be covered. Buckets can be used to protect these plants.
Covering vegetation allows the plants to tap into the warmth of the soil and underlying Earth, keeping it just warm enough to prevent frost damage.
Be sure to remove the coverings quickly in the morning hours. Sunshine can quickly warm the vegetation, and the covering could damage the plant.
Also, don’t forget about your pets and outside livestock. With morning lows in the mid 30s, outside animals will need some basic shelter and water for the overnight.
Frost is yearly occurrence in Northeast Florida and Southeast Georgia, but some simple steps could help protect your garden and your plants and animals.