You need to cover plants tonight if the forecast low is 36°F or lower, because leaves can frost while the air still reads above 32°F.
Cover Plants Tonight by Forecast Low
Check tonight’s low for your exact location on the National Weather Service forecast page (weather.gov, enter your ZIP code). Use the overnight low, not the daytime high, and look at the hourly graph to see how long the temperature stays down.
| Forecast low | What it means | Action |
|---|---|---|
| 37°F and above | No frost risk | No cover needed |
| 33–36°F | Frost can still form on leaves | Cover tender plants |
| 29–32°F | Light freeze | Cover tender plants; hardy cool-season crops need no cover |
| 28°F and below | Hard freeze | Cover everything you can and bring pots inside |
Frost is ice crystals forming on surfaces at about 32°F. A freeze is when the air itself reaches 32°F or lower. A hard freeze, 28°F or lower, is cold enough to kill the tissue of most garden plants.
Which Plants Need Cover and Which Can Skip It
Tender plants are warm-season crops and annuals. Hardy plants are cool-season crops and dormant perennials that handle a light frost. Sort what you have into one of these groups:
| Group | Examples | Cover when the low is |
|---|---|---|
| Tender | Tomatoes, peppers, squash, beans, basil, most summer annuals | 36°F or lower |
| Borderline | Peas, kale | 32°F or lower |
| Light-frost tolerant | Lettuce, broccoli, onions, cauliflower | 28°F or lower |
Cool-season vegetables such as cauliflower and lettuce generally come through a light frost and only get into trouble when temperatures fall into the 20s. If the low only dips into the 30s, these hardy plants are fine.
Exact tolerance varies by species and variety, and by how long the plant has been outdoors. Your local cooperative extension office can tell you how a specific plant in your region handles cold. Search for your state’s extension service and your county.
Why Frost Can Form When the Forecast Says 36°F
The forecast low is the air temperature about 5 feet off the ground. Leaves and soil surfaces lose heat to the open sky and can sit a few degrees colder than that. This is why frost shows up on mornings when the forecast never said 32°F.
Three conditions raise the risk:
- Clear sky: with no clouds, heat radiates straight out overnight.
- Calm wind: still air lets cold settle onto the plants. A steady breeze mixes the air and keeps leaf temperatures closer to the forecast.
- Low spots: cold air drains downhill and pools in hollows and at the bottom of slopes.
A cloudy, breezy night at 36°F is much less risky than a clear, still one at the same number. Covering costs little, so cover prized plants either way.
Also consider how long the cold lasts. A single night with a few hours below freezing is easy to cover through. A run of cold nights calls for covers that stay on and a plan for the daytime, as covered in the FAQ below.
How to Cover Plants Tonight Step by Step
- Water in the morning or afternoon. Moist soil holds and releases more heat overnight than dry soil. Do not soak plants right before dark, since wet foliage freezes more easily.
- Gather breathable covers. Bedsheets, blankets, towels, burlap, frost cloth or row cover all work. Cardboard boxes and upturned buckets suit small plants.
- Set up supports. Push in stakes, tomato cages or hoops so the cover tents above the foliage. Fabric resting directly on leaves can pass the cold straight through.
- Drape late in the afternoon. Put covers on before sunset, while the ground still holds the day’s warmth, and let them trap it.
- Reach the ground. Let the fabric hang all the way down and weigh the edges with rocks, bricks or soil. Gaps let the warm air escape.
- Remove covers the next morning. Take them off once temperatures climb above freezing and the frost has melted, so plants do not overheat under a sunny cover.
Avoid bare plastic. It conducts cold to any leaf it touches and traps moisture. If plastic is all you have, hold it clear of the foliage with stakes and put a sheet or blanket underneath. Take it off first thing in the morning, since plastic heats up fast in the sun.
If you use string lights or a lamp under a cover for extra warmth, use outdoor-rated cords and fixtures, and follow the manufacturer’s instructions for keeping bulbs away from fabric.
Potted Plants, Mulch and Raised Beds
Plants in containers lose heat faster than plants in the ground because cold hits the pot from all sides. Move tender pots against the house wall, under an eave or into a garage or porch. For a hard freeze, bring them indoors. Group pots together and wrap the pots as well as the foliage.
Larger pots hold more soil and stay warm longer, which is one reason to check what size plant pot you need before the cold season.
For in-ground beds, spread 2 to 3 inches of straw or mulch around low-growing plants, keeping it off the stems. Mulch slows the loss of soil heat. Apply it before the cold night, not after.
Established shrubs and dormant perennials are usually left uncovered. Cover them only when a hard freeze is forecast and they have tender new growth or buds.
If You Have No Covers, and What to Do the Next Day
With nothing on hand, tent cardboard, newspaper or towels over stakes, or turn a bucket or pot upside down over each small plant. Weigh it down so it does not blow off.
Harvest ripe tomatoes, peppers and squash before a hard freeze rather than trying to cover everything.
The next morning, check plants once frost has melted. Damaged leaves look dark, water-soaked, limp or wilted. Do not prune right away, because it takes a few days to see which stems are actually dead. Wait until new growth appears, then cut back to healthy tissue.
Related reading: The Best Plants for Flower Boxes of 2026 · The Best Plants for Concrete Planters of 2026
Frequently Asked Questions
Does a cover work if it’s windy?
Yes, if it is anchored. Wind can blow a cover off or let warm air escape, so stake it and weigh the edges down with rocks, bricks or soil. A steady breeze also tends to keep leaf temperatures closer to the forecast.
Should I cover plants if it only dips to 34°F for an hour?
Tender plants are still worth covering, since a cover costs little and a clear, calm night can leave leaves colder than the forecast air temperature. Hardy plants like lettuce or broccoli do not need it.
Do I cover newly planted seedlings differently?
Seedlings are tender and small, so cover them whenever the low is in the covering range. Use a bucket, pot or cardboard box, or a fabric tent on stakes, and weigh it down so it does not blow off.
Should I spray plants with water after a frost?
No. Let frost melt naturally as the sun comes up. Spraying does not repair damage and can chill leaves further. Wait a few days before judging which growth is actually dead.
Where do I find my average last and first frost dates?
Your local cooperative extension office publishes frost-date guidance for your county. NOAA’s National Weather Service gives tonight’s forecast low. Use the extension dates for planning and the forecast for tonight’s decision.
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