Overnight lows this week are forecast to drop below freezing across the region, so tender plants need to be protected.
In some areas of Nebraska, temperatures could drop below freezing tonight, but the worst night is forecast for Thursday.
The National Weather Service has issued a freeze watch for south-central to east-central Nebraska because of the potential for a hard freeze.
So far, Omaha is not included in the area expected to see a killing freeze, but the forecast can change.
Among the currently forecasted lows:
Omaha: 34 degrees tonight, 31 degrees Thursday night, and 34 degrees Friday night.
Lincoln: 36 degrees tonight, 27 degrees Thursday night, 33 degrees Friday night.
Kearney: 31,degrees tonight, 29 degrees Thursday night, 34 degrees Friday night. Norfolk: 31 degrees tonight, 26 degrees Thursday night, 34 degrees Friday night.
Kathleen Cue, horticulturist with the University of Nebraska-Lincoln Extension for Douglas-Sarpy Counties, says vulnerability to freezing temperatures varies with the type of plant:
• Emerging grass, spinach, lettuce and other cool-season plants should be fine.
• Tomatoes and peppers already in the ground should be covered. Even with protection, growth probably will be slowed the rest of the season due to root damage caused by cold soil. This is why people are encouraged to wait until at least Mother's Day to plant tomatoes or peppers.
• Tomatoes, peppers and other warm season vegetables still in pots should be brought indoors.
• Recently purchased trees and shrubs in containers should be moved to shelter if possible, even those species considered native to this region. This is because they're probably more accustomed to a greenhouse environment and haven't yet hardened off, Cue said.
• Petunias, impatiens, begonias and other annuals still in pots should be brought indoors; if they've been planted, they need to be covered.
• Tropical plants such as canna, elephant ear, cally lily should be brought indoors. These plants do not tolerate temperatures below 40 degrees.
Flowering fruit trees could suffer frost damage, too, she said.
If fruit tree flowers are singed by frost this week, the tree will drop the petals and not allow those blossoms to mature into fruit, she said. Interior blossoms on the trees may be spared damage, depending upon how cold it gets and how long during the night the cold lasts.
To protect outdoor plants that can't be moved indoors, cover with a couple of layers of sheets or a blanket, Cue said. Avoid using plastic or tarps because they plastic easily transmits the cold air, so any leaves touching the tarp will get nipped. The morning after a frost, do not remove the sheets until at least midmorning.
Continued, overall below-normal temperatures are forecast for the next couple of weeks, so a chance for additional 32-degree or lower nights are possible, said Barbara Mayes, meteorologist with the National Weather Service.