Tomato Temperature Tolerance – A Complete Guide

It is not uncommon for even the most seasoned gardener to become excited with the first sign of warm spring temperatures and plant their tomatoes outside too soon. Northerners sometimes expect to experience the first frost during prime tomato harvest time.

On the other end of the spectrum, those in hotter climates may be used to responding to heat stress when temperatures become unbearably hot for their tomato plants. Regardless of where one lives, many geographical areas require gardeners to address unpreferable temperatures at some point during the growing season.

One way to avoid common tomato temperature tolerance issues is to follow the best planting schedule and practices for the growing zone in which you live. We will explore tomato temperature tolerance and solutions further throughout this article.  

The ideal growing temperature for most tomato varieties is between 55 and 85 degrees Fahrenheit. Because tomatoes prefer such warm temperatures, gardeners typically start their tomato plants from seed do so indoors near a well lit window or with grow lights.

Regardless of how you start your tomato plants, it is recommended not to move them permanently outdoors until the day and night temperature stays above 55 degrees.

This is said to be after Mother’s Day in many seasonal growing zones. In addition to overly cold temperatures, the extreme summer heat can also damage tomato plants. It’s important to always address when temperatures drop or exceed the preferred range to keep your tomato crop healthy with a bountiful harvest.  

Read on to learn more about low, high, and ideal temperatures on tomato plants.  

Tomato Reactions to Variation in Temperature

While tomato plants are known for several growing sensitivities, the temperature is one of the most important. As mentioned previously, tomatoes will thrive when grown within a 30 degree range of 55 – 85 degrees Fahrenheit.

Suppose tomatoes are exposed to too cool or too hot temperatures, especially over extended periods. In that case, this can adversely affect the health of your plants and harvest production. Review the table below to learn how specific growing temperatures can affect your tomato crop:

Growing Temperature	Effects on Tomato Plants
28 degrees F	Tomato plants exposed to temperatures below freezing (32 degrees Fahrenheit) will most likely not survive unless that exposure is extremely brief.  Minor frost will damage the plant but any major frost will kill it.
35 degrees F	While tomato plants will survive in above freezing temperatures, exposing them to any temperatures near freezing will stunt their growth, damage the plant’s stem, vines, leaves and negatively affect the harvest.  This cold of temperatures is also known to negatively affect the plants production of pollen which can result in scarred or deformed (cat-faced)  fruit, and a smaller harvest.
42 degrees F	Temperatures in the low to mid 40’s will result in similar effects described at 35 degrees, but those effects will most likely be less severe, especially if the exposure to 42 degrees is brief.
50 degrees F	While a low temperature of 50 degrees is almost within the tomato’s ideal temperature range it can still minimally show some of the effects described previously, in addition to causing delays in growth and fruit production.  These effects are more likely if plants are exposed to 50 degree lows regularly.
58 degrees F	Consistent overnight lows of around 58 degrees will not negatively affect a tomato crop but will most likely benefit the plants and harvest production.  This is almost the lowest regular temperature threshold you want your tomatoes exposed to long term and provides a nice cooling off period for the tomato to hydrate and absorb nutrients more easily after the heat of the day.
70 degrees F	This is the sweet spot, falling almost smack in the middle of the ideal tomato temperature range.  Tomatoes will flourish in 70 degree temperatures, especially if the sun is shining.
85 degrees F	This is the peak hot temperature ideal for tomatoes.  Tomato plants will remain healthy with bountiful harvests at 85 degrees.  Cooler evening temperatures combined with this peak heat will only positively affect the health of tomato plants.
90 degrees F	While brief exposure to 90 degree temperatures on the hottest of summer days will probably not affect a tomato plant too tremendously, extended exposure to these temperatures can result in heat stress of the plant.  Heat stress is identified through browning of leaves and vines as well as delayed, or permanently stalled, plant development and harvest.

Read on for tips on protecting tomatoes from extreme temperatures:  

Tips For Protecting Tomatoes From Extreme Cold

Most seasoned gardeners know and follow planting schedules for the growing zone in which they live. However, it’s not entirely out of the ordinary for an unexpected, late-season cold snap to take one by surprise, even when following the local planting schedule correctly. When this happens, there are several options a gardener may take to protect their tomato crop.  

Move Plants Indoors

For gardeners who start their seeds or transplants in containers earlier in the season and those who are solely container gardeners, one of the most effective responses to a cold snap can be to move tomato plants in containers to an indoor, climate-controlled location.

Lighting is also important if tomatoes need to be indoors for an extended period. Grow lights are becoming more and more popular with at home gardeners and can help your tomato plants stay on a normal light schedule for longer cold snaps. If grow lights aren’t possible, then a well lit window location will suffice for keeping tomatoes healthy indoors short term.   

Cover Plants Outdoors

Suppose tomato plants are already planted in the ground, or it’s not conducive to move containers indoors. In that case, another option to protect your tomato plants from cold temperatures is to cover them.

There are various options to cover tomatoes and keep them warm enough to survive a cold snap. A tarp or sheet is typically what is most easily available to them at home gardeners and does a great job protecting tomatoes from the cold as long as it’s not near freezing for more than a few days or nights.  

Interestingly enough, bubble wrap is known to be a very successful cover material for tomatoes and other plants when cold temperatures arrive. The bubbles provide an extra layer of insulation from the cold, keeping the plant temperatures warmer. So the thicker the air bubbles, the warmer your plants will be. Also, because bulk bubble wrap is sold in rolls, it can easily cover larger growing areas.  

Another solution for larger growing areas is hoop houses. Many farmers find hoop houses to be the ideal option for covering tomato plants. Hoop houses can be stored in small areas yet extend to cover long rows of tomatoes or other crops. Some include closures on the ends for extra insurance that plants stay warm during unseasonably cold temperatures.  

Regardless of the material that you have available, covering tomatoes when temperatures dip near freezing is crucial to their health and harvest.  

Harvest Fruit Early

In some colder temperature growing zones, tomatoes are thriving in harvest as the first seasonal frosts start to arise sporadically. In the growing season, tomato plants may be too big to cover fully, but you can still protect your harvest by picking all of your almost-ripe tomatoes to finish ripening indoors before the cold can affect them.

Harvesting your fruit before a cold snap and then covering what you can of the plant are a great combination to protect your tomato plant and prolong its life.  

Tips For Protecting Tomatoes From Extreme Heat

Depending on the growing zone in which one lives, extreme heat can become a concern during prime tomato growing season. If tomatoes are exposed to extremely hot conditions for more than a day, it’s essential to take action on at least one of the following tips to protect your plants and harvest. 

Mulch

Mulching is a preventative measure that can help protect tomatoes from extremely hot conditions. It is unrealistic to plan to mulch when an unexpected heatwave arises, but it is valuable to integrate mulching into your annual spring planting cycle before hot conditions arrive.

There are a variety of materials that can be used for mulching. Some include compost, chopped leaves, straw, shredded bark, or sawdust. Visit your local garden center to determine what mulches are available in your area that are also beneficial to tomatoes and other plants in your garden. Many garden facilities will deliver large mulch orders to your home for a fee.  

Hydrate Generously 

Watering tomato plants in the evening, after the heat of the day, has passed, is always best practice. In conditions of extreme heat, this routine is even more critical. If a heatwave continues over multiple days, it is also recommended to add a morning watering until daytime high temperatures drop to 85 degrees Fahrenheit.

Even though some of the moisture in the morning water may be evaporated by the daytime sun, it is also likely that your tomato plant will absorb some moisture to help it get through an unnaturally hot day.  

Create Daytime Shade

As with most living things, shade effectively protects tomato plants from extreme heat. Moving your tomatoes into a shaded environment may be simple if container gardening. For tomato crops rooted in the earth, creating shade may require a bit more effort and creativity.

When designing a shade setup for tomatoes, remember that even though the goal is to protect them from the heat, they still need some sun. Figuring out shade that can protect plants from the hot sun during the heat of the day, noon to 4 or 5 pm, in most areas, while still exposing the plants to morning and late afternoon/evening light is ideal.

Knowing the direction the sun hits the tomatoes throughout the day is helpful before designing your shade structure. Materials that have been known to provide shade for tomatoes in extreme heat effectively include umbrellas, tarps, stakes, and even strategically placed lawn furniture.  

Harvest Fruit Early

While most gardeners live for vine ripened tomatoes, as with extreme cold, it is best to harvest tomatoes a bit early if a heatwave is expected. Combining this practice with shade, mulch, and generous watering will result in a healthier tomato plant and harvest despite hot conditions.  

Helping Tomatoes Recover From Extreme Temperatures

Ideally, if tomatoes are exposed to extremely hot or cold temperatures, it is not for an extended period. With shortened exposures to these unideal growing temperatures, it is more likely the plant will recover with a little help from its gardener.  

While tomatoes exposed to low intensity frost may survive, there is still damage to be addressed. Initially, moving the tomato out of any still frosted conditions while also enacting any of the protection tips shared previously is crucial.

However, to support the plant’s long term development, it is also best practice to prune any damaged leaves, vines, or fruit. Depending on the level of exposure, this could mean a heavy pruning, but this is the best bet on your tomato plant continuing to live a healthy life with a bountiful harvest.  

A plant with heat stress will exhibit signs through dry, browned leaves or vines and dropped flowers. It’s important for heat stressed plants to have some recovery time before heavy vine growth or fruit development.

Gardeners can help with this recovery time by harvesting any heavy fruit for indoor ripening and pruning other heavy parts of the plant. In addition, do not fertilize the plant with any growth nutrients until it has fully recovered from the heat stress.  

Specific Tomato Variety Response to Temperatures

In general, most tomato plants will thrive in those ideal growing temperatures of 55 – 85 degrees Fahrenheit. However, some tomato varieties grow with more success in cooler temperatures, and others are known for being more tolerant of hotter temperatures.  

Read on to learn which tomato varieties are more temperature tolerant:

Tomato Varieties For Colder Temperatures

The tomato varieties that are most tolerable to temperatures colder than 55 degrees Fahrenheit are short to mid-season tomatoes that mature faster than other varieties. There are too many cold-tolerant tomatoes to list them all, but here are some popular and lesser-known varieties:

Variety	Fruit Description
Early Girl	Medium sized round, bright, juicy
Golden Nugget	Small, round or oval cherry, bright, sweet, yellow orange
Bush Beefsteak	Medium to large, round, meaty, deep red
Sugar Baby	Tiny, round cherry, extra sweet, orange

Tomato Varieties For Hotter Temperatures

Typically tomato varieties that are more tolerant of temperatures hotter than 85 degrees are also more tolerant of drier climate conditions than other varieties. Some of the heirloom varieties that do well in cold temperatures also tolerate hot temperatures; the Early Girl is an example of this. While there are too many heat-tolerant tomatoes to list them all, here are some well known and less common varieties:

VarietyFruit DescriptionPhoenixLarge to extra large, round beefsteak, very flavorful, bright redGreen ZebraMedium, round, sweet yet tart, pale green with darker stripesFlamencoSmall to medium, round, juicy, fiery redHomesteadLarge, round, soft beefsteak, Savery, dark red

Final Thoughts On Tomato Temperature Tolerance

Whether you are addressing issues with extreme temperatures or preparing for them, being conscious of the weather patterns in your location will help in growing tolerant tomato varieties that will be most comfortable in your garden.

It is more likely that a gardener in Maine will follow different practices than a gardener in Arizona in protecting their tomato crop from extreme temperatures. Being educated and prepared for conditions common to your growing zone will likely result in a happy tomato harvest.