CHARLOTTE, N.C. — The National Weather Service has issued a Freeze Warning and Frost Advisory for much of western North Carolina.The late-season cold snap could threaten plants as it continues through the Mother's Day weekend, where temperatures Sunday morning could be near 40 in Charlotte and 30 in Boone.
"It's the temperature of the surface that matters most," WCNC Charlotte Chief Meteorologist Brad Panovich explains.
During the day, solar radiation, in the form of heat, raises the temperature of surfaces such as grass, dirt, and pavement. Then at night, those surfaces release the heat back into the atmosphere.
"That's what if your plants are near the house, they'll do pretty good," Brad explains. "They'll be receiving the excess heat from the building materials."
Plants away from the home may struggle during cold weather.
"The more view of the open sky you have, the more you're going to see frost in that location," Brad explained. "And without any adjacent heat sources, those plants may struggle in the middle of the night.
Frost can form even with air temperatures of 33-38 degrees, which are likely across western portions of the Carolinas this weekend. The temperature near the ground due to radiational cooling can be much lower.
Here's what you can do to protect those plants:
- If you can bring them inside the garage or house or even onto the porch. Anything closer to the house will help. All objects reflect or emit longwave radiation which can keep plant warmer. Beds and gardens farther from the house and trees will get the coldest. An open sky is bad this allows from the maximum radiational cooling so protect those plants first. Basically, the more sky that plant can see the colder it will get at night.
- Today when the sun is high in the sky water your plants heavily. This water will help absorb heat today and trap it in the soil and plant. This will work much better than you think. Not only will the ground absorb heat the plants will as they suck up the water. Then at night the plants and soil that have more moisture cool much slower than dry soil and plants. This worst great for frost or light freeze set-ups.
- You can heavily mulch your beds with leaves, straw or mulch to help protect the plant. The key here is to do this during the heating of the day you want to trap as much heat from the sun in the ground, mulch, and plant during the day, so that has it for tonight.
- Then of course, once the sun goes down cover your plants. The best materials are fabrics and not plastics. If you cover them soon after sunset, you will trap the maximum amount of heat for tonight. Be sure though to uncover them as soon as the temperature warms in the morning or the sun gets higher in the sky. Leaving them covered with the sun up can cause damage as well. Never use plastic if at all possible this will cause damage.
Brad talked about protecting your places on Friday's Weather School, our weekday, science lessons for kids and students at home during the COVID-19 coronavirus pandemic.
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