Cold Stress Calendar for Crops

Cold stress is not one event. It is a run of risks that changes with the crop, the growth stage and how long the cold lasts, so a useful calendar tracks all three.

Key points

Cold stress includes freeze injury and chilling injury, and duration matters as much as the number on the thermometer.
Group crops by tolerance and by growth stage, not by name alone.
Use freeze probability tables as risk levels, then choose the level that fits your tolerance for loss.
Record every cold event so your calendar reflects your own fields.

What is cold stress and how is it different from frost?

Cold stress covers any damage a crop takes from low temperatures. Frost and freeze injury is the part most growers know: ice forms in or on plant tissue and kills cells. Chilling injury is quieter. It happens above freezing, when cold soil or cold water slows or scrambles normal growth, especially in seeds and young seedlings.

Extension writers often describe a frost as air near 32 degrees F, where water begins to freeze on low surfaces, and a hard freeze as somewhat lower, roughly the upper 20s to about 31. Damage depends on temperature and on how many hours the cold lasts, so a brief dip and an all-night freeze are different problems.

How cold can different crops tolerate?

North Carolina State Extension groups vegetables into rough tolerance classes. Warm-season crops such as beans, corn, cucumbers, peppers and tomatoes are damaged or killed at about 31 to 33 degrees F. Cool-season crops such as broccoli, cabbage, lettuce, onions and radishes can take a hard freeze for a limited time, though leaves may be damaged and later yield can suffer. The hardiest group, including Brussels sprouts, beets, collards, kale, parsley and spinach, is expected to survive temperatures below 26 degrees F during a longer hard freeze.

Warm-season crops: plan around the first light frost, not the first hard freeze.
Cool-season crops: plan around how long the cold lasts and how developed the plant is.
Hardiest crops: plan around soil freezing and harvest access.

What does chilling injury look like in seeds and seedlings?

Penn State Extension describes imbibitional chilling in corn and soybeans. Seed takes up water in the first day or two after planting, and if that water is cold, cells can rupture. The risk is highest when soil at seed depth is below about 50 degrees F during that window. Corn roots and shoots may fail to develop properly, and soybean cell membranes may not hydrate correctly.

You cannot fix seed that is already in the ground. After a cold rain or a long cold stretch, scout for uneven or missing emergence instead of waiting for the damage to show up in yield.

How do you build a cold stress calendar for your farm?

Start with your own records. List every crop you grow and its most cold-sensitive stage: germination, transplant establishment, bloom, fruit set or harvest. Then attach a threshold temperature to each stage using your extension service guidance. Finally, pull local freeze probabilities from NOAA or your regional climate center and mark the 10, 50 and 90 percent dates for the thresholds that matter to you.

For example, if your local spring record shows a 36 degree F frost about one year in ten after a certain date, you might hold tomato transplants until after that date, while planting spinach weeks earlier. The point is to link each crop to a threshold and a risk level you are willing to accept, then let the calendar follow.

Column one: crop and stage.
Column two: damaging temperature and duration.
Column three: local date at your chosen risk level.
Column four: protection you have on hand.

What can you do before a cold night?

Moist soil holds heat and releases it slowly, so a properly watered field often fares better than a dry one. Avoid cultivating right before a freeze, because loose soil loses heat faster and root damage adds stress. Row covers work well on small plantings if you check the temperature underneath and remove them before heat builds the next day.

Overhead irrigation can protect crops, but it needs large volumes of water and must run continuously through the whole event, which many vegetable operations are not set up for. Check local water rules before relying on it. Moving frost-sensitive transplants indoors or simply delaying transplanting is often the cheapest protection.

What mistakes cause avoidable cold losses?

The most common error is trusting a single date. A date from a table is an average of past years, not a forecast. The second is ignoring cold pockets: cold air drains downhill and settles in low spots, so one corner of a field can freeze while the rest escapes. The third is skipping the check after the event. Walk fields a day or two later, because injury sometimes takes time to show.

Keep notes on every cold night: lowest reading, crop stage, and what you saw afterward. Over a few seasons those notes become the most accurate cold stress calendar you can own.

When to get local help: Ask your county extension office or a certified crop adviser which temperature thresholds apply to your crop varieties and growth stages, and what protection methods suit your scale.

Sources and further reading

Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.

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