Fruit Tree Chill Hours: What Are They?

What are fruit tree chill hours, and why do they matter? We're explaining how chill hours work so you can plan your food forest!

Written by Lorin Nielsen Last updated: February 25, 2026 | 6 min read

Two individuals in green jackets use ladders to trim brown, leafless branches in a snow-dusted orchard, showing fruit tree chill hours

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For many gardeners, the idea of having a lovely small orchard of nut and fruit trees is a major enticement. But before you can start that food forest, you have to do a little extra planning so you know the fruit tree chill hours for the varieties you want.

Why do chilling hours matter? Is there a reason you couldn’t just plant any tree anywhere? Are people in very cold or warm climates going to have problems with their trees? And how can you guarantee good fruit production in low chill regions?

Let’s explore the concept of annual chill hours and provide some insight for you to use when you plot out your future grove of tasty delights!

Gala Apple Tree

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Gala Apple Tree

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Improved Meyer Lemon Tree

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Hardired Nectarine Tree

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What Does Chill Hours Mean For Fruit Trees?

Winter snowy garden with dormant or dead trees and shrubs, showcasing bare branches and dry, brown leaves. — Some trees need cold to trigger fruiting.

For both fruit and nut trees, there is a period of dormancy over the winter. During that dormant period, most fruit or nut varieties need a certain amount of winter cold. “Chill hours” describes the number of hours of cold temperatures a tree receives between October 1st and late February.

The “below 45” standard is what most nurseries use to set chill hours and consists of cold weather that drops below 45°F (7°C). Optimal “below 45” weather falls between 32 and 45°F (0 to 7°C), when there’s no risk of frost or freeze damage to the tree itself, but in areas that do get annual snow, the cold winter weather is included in the chill hours.

As you can imagine, chill hours can rapidly increase the further north in the United States you go. Somewhere like sunny San Diego is typically considered to have low chill hours, usually 500 or fewer between October 1st and February 28th, and will usually be in the optimal range of the “below 45” scale, though it’s rare to have more than the occasional frost there.

In contrast, somewhere like Seattle is likely to have closer to 1,200 to 1,400 chill hours in that same period. Orlando, Florida will likely have under 100 chill hours most winters!

What Happens if a Fruit Tree Doesn’t Get Enough Chill Hours?

In the winter garden, leafless Peach trees stand against the backdrop of a vibrant green lawn, their bare branches creating intricate silhouettes against the clear sky. — Cold conditions in an almond orchard.

Fruit trees can thrive in both cold and warm temperatures. But if you want good fruit production, you need to make sure you get enough annual chill hours for the varieties you’re growing.

The number of chill hours relates to the dormant season and plant hardiness. As fall sets in, a deciduous fruit tree absorbs the nutrition stored in its leaves. This causes the lovely fall display of dropped leaves that occurs every year as those leaves, no longer needed, fall from the branches. The tree weathers the winter cold on a limited amount of nutrition until warmer temperatures return.

Because of this, the plants have adapted to a certain schedule. They need enough energy to survive through a certain number of chill hours over a period of months before breaking dormancy in spring. If they don’t reach the expected number of chill hours at those minimum temperatures, bud break for the next season’s foliage may be delayed. If flowering doesn’t happen when it’s supposed to, the tree may not have a very productive year. Alternatively, it may still produce but considerably later than trees with lower chill hour requirements.

Non-Deciduous Trees

There are also many fruit trees that aren’t deciduous, like citrus. These go somewhat dormant for the winter but still receive passive nutrients via photosynthesis through their leaves. Many citrus varieties, such as clementines or mandarin trees, have produce still on the tree well into winter.

Typically, non-deciduous fruit trees have lower necessary chill hours, and as a result, they grow extremely well in areas like Southern California or other southern regions across the United States. While these low chill varieties are an option, you definitely don’t want to put them outdoors in a high chill area!

Chilling requirements vary widely between species. Check your average chill hours before selecting your fruit trees to be sure you have enough to satisfy their specific needs. Trees that need higher chill hours than your region can supply may not grow as well in your area. There are trials underway on growing high chill varieties in low chill locations, and there may be some potential for that in the future.

Can Cooler Temperatures Affect Fruit Set?

Tree branches are covered with a thick layer of ice in the winter garden. — Cold-damaged parts drop from the tree and fall to the ground.

One might assume that if they have enough chilling hours for a tree, they’re going to have an abundance of produce. But it’s not quite that simple, unfortunately.

Remember how different varieties are adapted to certain periods of cold weather? If you take a tree that’s used to about 700 chill hours throughout the winter, it’s not going to perform great in Florida. But it may also struggle in cold climates like Seattle, where there are far more chill hours.

If low chill temperatures are met in early winter in cooler northern climates, and yet there are still months of chilling hours to come, the tree may believe the worst of the cold is already over. An early warm spell can cause it to spring into life and start producing flower and fruit buds. If the weather suddenly turns cold again, all set fruit can be damaged by frosts and freezes. Flowers can drop off trees, set fruit can blacken and fall, and tender new growth will be seriously impacted. Fruit and nut production can decline as a result.

There are always years when a freak frost comes through during the wrong season. In 2022, a sudden frost hit at the time many commercial almond growers in northern California were seeing bud break and flowering. This caused a severe blossom drop and a much smaller fruit set than in prior years, likely impacting the eventual harvest for many nut tree growers in the region.

Bottom Line: Don’t Ignore Chill Hours

It can’t be stated strongly enough that the chill hour requirement is important. It’s critical to pick a fruit tree variety that can handle the winters in your area. Areas where freezing temperatures are common every year will require higher chill varieties than warmer climates. Even then, there’s always a chance that if the weather warms above 45°F (7°C) unexpectedly early, a freak cold burst could still cause problems.

We can’t control the weather, but we can control what trees we plant! It’s also not just tree fruit to consider. Other plants, such as cane fruit like raspberries, can also have chilling requirements. Pay attention to the variety you’re considering and whether it’s generally considered to perform well in your USDA zone.

Fruit Trees Chill Hour Requirements

Close-up of branches with drooping, pale brown, oval leaves featuring jagged edges, all covered in a layer of frost. — Check information about chill hours according to your region.

With all fruit and nut trees, we highly recommend checking your zone and making sure you have varieties with the right chilling requirements for your region. While a low chill tree will perform well in most of the southernmost United States, it may have serious issues in significantly colder areas of the central or northern US.

We’ve provided a list of some of the most popular varieties and their approximate chill hours, but remember, different cultivars have different needs!