Updated at: 05-10-2022 - By: Sienna Lewis

When it comes to building a greenhouse, many gardeners are curious: “How hot can a greenhouse get?” In order to cultivate healthy plants, you’ll need to know how to keep your greenhouse at the ideal temperature and humidity.

One of the best aspects of greenhouse gardening is that you can completely control the atmosphere in which your plants grow. The temperature inside the enclosure is an essential consideration. You’ll need to know how to control the heat generated by the sun’s rays if you want to keep your greenhouse’s temperature between 80 and 85 degrees Fahrenheit.

Like a car, your greenhouse needs regular maintenance. On a sunny, warm day, temperatures can soar to well over 100 degrees Fahrenheit very rapidly. Because of this, it’s best to regulate the temperature before your plants are harmed and killed.

What Temperature is Too Hot for a Greenhouse?

When the temperature reaches 90 degrees Fahrenheit, you know it’s too hot for your greenhouse. Tomatoes, even the hardiest of veggies, won’t do well at temperatures this high since they will simply lose the water they require to survive.

When your plants’ leaves droop or if they lose some of their leaves in an attempt to save water, you know they’re suffering in the heat. As previously stated, you must maintain a temperature between 80 °F and 85 °F for optimal plant growth.

How Hot Can a Greenhouse Get - Krostrade

Do Greenhouses Work in Hot Climates?

They do indeed. In locations where the environment is hot, a greenhouse is the ideal option to keep your plants flourishing all year round.

It is recommended to reduce heat gain, add shade cloth, utilize an evaporative cooler, and a mechanism that transfers heat from the earth to the air when the outdoor temperature exceeds 100 °F. Your greenhouse will not overheat as a result

What Temperature Should a Greenhouse be At Night?

Most of your greenhouse plants will like it if you maintain the temperature down to 75 degrees Fahrenheit at night. However, it’s vital to keep in mind that some crops perform better when grown in milder greenhouse conditions, such as peppers and tomatoes.

How Do I Cool Down My Greenhouse?

Make sure your greenhouse is properly vented to keep it cool. If you employ roof vents, louvered side vents, and the greenhouse door, your hot plants will find relief. Having one-fifth of your floor surface devoted to roof vents will ensure that your plants get a thorough air exchange every two minutes or so.

Can a Greenhouse Get Too Much Sun?

In particular in the summer, yes. Fans and roof vents are essential in ensuring that your crops don’t suffer from overheating. Some gardeners end up scorching their plants in an effort to maximize the amount of sunlight they can get into their greenhouse.

What Plants Can Survive Extreme Heat?

Several heat-loving plants, such as geranium, lantana, sedum, cosmos, marigold, lemon verbena, and lantana, can keep a garden looking lush and vibrant even during the height of the summer season.

Is it Much Better to Grow Your Plants in a Greenhouse?

That’s correct. It is considerably better for you and your plants to engage in greenhouse gardening as opposed to typical outside gardening. Here are some of the explanations:

It serves as a haven for your plants

A greenhouse provides a safe haven for plants that would otherwise be at risk from damaging pests and animals in an ever-changing external environment. As a result, greenhouse gardeners won’t have to spend time preparing for weather-related emergencies like severe rains or blizzards. In addition, you can keep destructive pests out while allowing beneficial insects in with greenhouse gardening.

You can take full control over your plant’s growing environment

An additional benefit of a greenhouse is that it allows you to cultivate the ideal growing environment for your plants. You’ll be able to regulate the humidity and temperature within the cage. Because even if it’s snowing out, your plants may thrive in a tropical atmosphere inside the greenhouse.

You’ll get to grow more plant varieties and extend their growing seasons

You’ll be able to lengthen the growing season of your plants in a greenhouse because they aren’t exposed to the weather outside. There is also the added bonus of being able to cultivate non-native plant species.

How does the type of plant affect what temperature is too hot?

It’s crucial to know your plants’ needs because the appropriate greenhouse temperature differs from one plant to the next.

It’s critical to understand the optimal temperature ranges for various plant types.

Keep an eye out for these details when you buy seeds for your greenhouse next time around.

Knowing if your plants can handle the heat is extremely crucial.

Heat-tolerant plants

At temperatures as high as 90 degrees Fahrenheit, some plants can still grow. The ideal temperature range for heat-tolerant plants is between 80°F and 90°F.

Summer crops are typically referred to as such since they are able to tolerate the heat and remain productive. Among them are the following:

A 90-degree Fahrenheit greenhouse is still too hot even for the plants listed above.

Photosynthesis slows down as the temperature rises above a certain level.

Make sure your greenhouse doesn’t get hotter than 90 degrees Fahrenheit by monitoring the temperature.

The plants on this list, on the other hand, are the most resilient.

So you don’t have to worry too much about this.

If you’ve never planted in a greenhouse before, are concerned about your greenhouse getting too hot, or have had problems with your plants in the past, these are the plants you should use.

How Does a Greenhouse Work? - Essential Home and Garden

Heat-sensitive plants

The plants that are most vulnerable to heat are the ones you need to watch out for.

Temperatures between 75 and 85 degrees Fahrenheit are ideal for these plants. Among them are:

My earlier list of “resident tough guys” didn’t include these plants.

If you want a good harvest from heat-sensitive plant kinds, you’ll need to lower the temperature in your greenhouse. 85 degrees Fahrenheit is too hot for heat-sensitive pants.

Summer is the time of year when most gardeners have issues with their greenhouses overheating, making it difficult for these plants to thrive.

So, if you’re craving beets and want to cultivate your own, keep in mind that temperatures beyond 85 degrees Fahrenheit are dangerous.

How does your location affect what temperature is too hot?

Make sure to keep in mind the weather in your area before making a decision.

People who live in hotter climes, for example, should pay special attention to how hot their greenhouses get.

Greenhouse owners in Alaska, on the other hand, will struggle to keep their structures warm enough.

However, there’s more to consider than just how hot or cold your climate is.

However, the temperature in your area isn’t the only factor to consider.

Plants often suffer fungal infections and mildew when exposed to conditions that are both hot and damp.

So, farmers in greenhouses, pay attention! The lower end of the recommended temperature ranges for your specific plants should be your goal if you reside in a hot and humid climate zone.

The South and Southwest of the United States, Mexico, India, the Philippines, and other countries have a hard difficulty keeping their greenhouses from overheating.

People living in these regions need not be concerned.

We’ll talk about how to keep your greenhouse cool later on in this piece.

How to check the temperature of your greenhouse

Basically, don’t buy a mercury thermometer at all. Just too many drawbacks!

Mercury thermometers are inaccurate and dangerous if they are broken, making them a poor choice for thermometers.

As a result, you should not use them to monitor the greenhouse’s temperature.

A thermocouple is the best way to get an accurate temperature reading.

What is a thermos?

You may not have heard of a thermocouple before, but they’re actually quite interesting (no pun intended).

Two pieces of metal are twisted together to form a thermocouple.

They generate a voltage in proportion to the difference in their temperatures.

What’s the end result?

Temperature measurement is simple, allowing you to get an exact reading of your greenhouse’s temperature.

So if you’re still itching to produce beets, you’ll want to stock up on that.

In order to acquire the most accurate reading, where should you set your thermocouple.

Sun and light should be kept out of your sensor.

The thermocouple will display an incorrectly high temperature if this is not the case.

The optimal location for the thermocouple is along a steady stream of air.

A simple way to meet these standards is to place your thermocouple in an enclosed box that is reflecting in color.

Placement of the thermocouple too high is another common error.

Keep in mind that heat rises. In this case, the thermocouple will read a few degrees higher than what your plants are actually experiencing.

In other words, the ideal location for your thermocouple is at or near the height of the plant.

Keep an eye on the greenhouse’s temperature with a thermocouple to catch it if it starts to get too warm.

If your thermocouple is still functioning well and is in a decent location, you should also check it.

How to lower the temperature in your greenhouse

What are you going to do with all of this information on how hot a greenhouse may get now that you have so much of it?

When it comes to greenhouses, there’s no need to succumb to the whims of Mother Nature.

In order to extend the growing season and increase crop yields, there are numerous techniques to lower the temperature of your greenhouse.

You can lower the temperature in your greenhouse by using the following techniques and methods:

  • System of ventilation
  • Fans
  • Shade
  • Watering
  • A calming effect
  • Fan misters and evaporative cooling
  • Undersea fan

Ventilation systems

A simple technique to keep your greenhouse cool is by using ventilation systems. Most greenhouses already have them.

How Does a Greenhouse Work? | LoveToKnow

Ventilation systems work by moving air through plants that have become too hot.

Proper ventilation and a decrease in greenhouse temperature can be achieved by opening your greenhouse door and other vents on the top and side walls.

This is a simple and inexpensive method for lowering greenhouse temperatures.


Ventilation systems and fans both work by creating airflow to cool your plants.

If your greenhouse’s ventilation system isn’t doing the trick, you may want to consider purchasing a fan.

Direct-drive fan units powered by solar panels are also popular and don’t require any electricity at all.


This is a simple one: shade lowers the temperature!

When it comes to creating shade in your greenhouse, there are many options available.

Creating natural shade in your greenhouse by growing plants with huge leaves and high canopies is a terrific idea.

Shade cloths can also be used.

When it comes to shade cloths and nettings, there are a variety of materials to choose from, but the best ones are made of aluminet, which does not heat up your greenhouse when the fabric gets hot.

Also, be sure to read the entire post to learn how much shade cloth to use.


You can’t lower the temperature of your greenhouse by watering your plants, but it is the most vital thing you can do for your plants in the face of high temperatures.

Transpiration, or sweat, is how plants regulate their internal temperature.

Plants, like us, lose moisture when they are exposed to heat and sunlight. They will perish if they are unable to sweat, as their body has no way of naturally combating the heat.

Damping down

This is an extremely easy technique for lowering the temperature of your greenhouse.

This is a simple method for decreasing greenhouse temperatures.

As a result, the rest of your greenhouse will get cooler due to the evaporation of the water.

Despite its simplicity, this method is extremely effective. As a bonus, it makes some pests more difficult to attract.

Evaporative coolers and fog misters

An electronic cooling system is another popular choice for dealing with the summer heat in a greenhouse.

These devices are powered by electricity and can be quite pricey.

A pad-and-fan system (also referred to as an evaporative cooler or swamp cooler) and a fog system are two of the most often sold options.

A mist system is another common choice for large greenhouses.

Only when all other solutions have failed do you need to resort to the most expensive ones.

Undersoil fan

In spite of its rarity, this method is extremely effective. You can think of it as greenhouse geothermal cooling.

Basically, you may buy a fan system that is buried in the soil and uses pipes to force hot air out of the greenhouse.

This, in conjunction with sufficient ventilation, will significantly reduce greenhouse temperatures.

With this method, the greenhouse’s warm air is cooled down by transferring its heat to the earth beneath it, which is much cooler than the greenhouse’s air (often approximately 55 degrees Fahrenheit).

Is this clear to you now? Now is the time to keep your plants cool throughout the hottest part of the year!

Monitoring Greenhouse Temperature

Install a thermometer in the greenhouse so that you can monitor the temperature at any given time. According to the University of Georgia Extension, most plants flourish in temperatures between 70 and 80 degrees Fahrenheit during the day.

Extreme heat shouldn’t be used on most vegetables; however, some may be able to handle it. According to the Ontario Ministry of Agriculture, Food and Rural Affairs, tomatoes will yield fewer fruit at temperatures above 95 degrees, and peppers will shed their blooms and generate sterile pollen at temps above 90 degrees.

To avoid wilting, water the vegetables more regularly as the temperature rises. Keep the soil moist, but don’t drown your plants by oversaturating it. According to Iowa State University Extension and Outreach, if you have an irrigation or automatic watering system installed in your greenhouse, you should check it periodically for leaks and plugged filters during the summer months.

Cooling Your Greenhouse

Summer greenhouse overheating is typically avoided thanks to good ventilation and fans in many locales. Vents should be installed on the roof or the walls of every greenhouse. Remove as many side and roof panels as possible and leave them open to allow heat to escape the greenhouse and improve ventilation throughout. The University of California, Davis recommends opening vents in your greenhouse to lower the temperature by up to 10 degrees depending on the weather and wind conditions outside.

Adding additional fans can help regulate temperature and airflow. If you want to keep your greenhouse cool, consider installing exhaust fans that draw hot air from the greenhouse and allow fresh air to enter. According to University of California, Davis, evaporative cooling is a more cost-effective method of lowering greenhouse temperatures by 20 degrees than using vents alone.

Avoiding excessive heat in the greenhouse can also be accomplished by providing shade from the sun’s rays. Consider putting your greenhouse in the shade of trees if you live in a hot environment. Installing shade cloths on the greenhouse’s outside is an alternative if this is not an option. Shade curtains can also be used on the inside of the greenhouse to protect the plants from direct sunlight.

Greenhouse Planting Guide

Growing veggies year round in a greenhouse still necessitates timing the planting of seeds. According to Iowa State University Extension and Outreach, planting cool-season vegetables like lettuce, cauliflower, and beets in the summer can harm the plants or hinder seed germination. For instance, lettuce will not sprout if the soil temperature is above 80 to 85 degrees. If the temperature rises too high, the greens may also grow blossom stalks and turn bitter.

The cool-season veggies should be completed producing by the time the hot summer weather arrives, and the hot-season vegetables should be prospering. PennState Extension recommends tomatoes, peppers, maize, beans, zucchini, and summer squash as heat-tolerant summer greenhouse crops to consider.

Even veggies from the warm season might be damaged by too much heat. Experts at Iowa State University Extension and Outreach say that tomatoes can be affected by issues like sterile pollen and blossom abortment as well as uneven ripening and sunscald damage.

Related Questions

How do you cool down a greenhouse?

Ventilation, shade, and evaporation are the three most common ways to keep a greenhouse cool.

There are various ways to go about this. You can open a window or vent for ventilation, or you may go fancier and use a fan.

It is possible to shade with shade nets and cloths, as well as with shading paints. A damper, evaporative chiller, or fog misters can all be used to evaporation.

How can I reduce the heat in my greenhouse?

When it comes to greenhouse cooling, the most frequent methods include the employment of evaporative coolers (such as misting fans with water), shade fabric, shade paint, and dampening.

Additionally, the evaporative cooling action of fog misters might be utilized as a seventh alternative.

How to regulate temperature in a greenhouse?

Heating and cooling greenhouses are necessary in order to maintain a stable temperature throughout the year (in summer).

Heating and cooling are accomplished through the use of evaporation and ventilation. Various methods are employed to keep the house warm: insulation, weather stripping, thermal mass, and heaters. As a result, greenhouse temperature control may be automated, making it simple and hands-off.

What level of humidity is too much for a greenhouse?

The humidity in your greenhouse must be managed in the same way that the temperature is.

Unfortunately, there is no perfect humidity range. Humidity levels in your greenhouse should be as high as possible in areas without any damp foliage. Fungal infections and mildew can be caused by wet foliage.

Final Thoughts on the Answer to “How Hot Can a Greenhouse Get?”

As vital as it is to know how hot a greenhouse may get, it’s more important to have complete control over the temperature and humidity levels within it. Your plants can be successfully cooled down with the help of roof vents and other cooling devices such as fans.