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Where do you measure temperature in a grow room?

Tom Starley
January 2, 2024
11 min read
An IR heat gun measuring the temperature of a cannabis leaf.
An IR heat gun measuring the temperature of a cannabis leaf.
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Just as a doctor checks your heartbeat, measuring the temperature in your grow room is essential for the health of your plants. 

It's not just about keeping things warm or cool; it's about creating an environment where your plants can flourish. 

In this post, we'll dive into the specifics of where and how to accurately measure temperature in your grow room, ensuring that your plants grow in a setting that's just right for them. 

Overview of grow room temperature

In the delicate art of indoor growing indoors, getting the temperature just right is a game changer. Especially for plants like cannabis, known for their specific climate needs. 

The impact of temperature in your grow space is profound. It's not just about survival; it's about allowing each plant to flourish in its own right. Optimal temperatures can lead to robust growth, enhanced terpene profiles, and improved resilience against pests and diseases. 

Conversely, incorrect temperatures can lead to a host of issues. These include wilting and weak growth to reduced yield and quality. 

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Key areas for temperature measurement 

If you’re trying to grow the best plants, knowing where to measure temperature in your grow room or grow tent is critical. 

Different areas within the same space can have varying temperature levels, affecting plant health and growth. Let’s look at the key spots:

An illustration showing at what height to hang a grow sensor next to a plant in a grow room

Canopy level

This is where the action happens and is the best location to place your sensor or hydrometer. For plants like cannabis, the canopy level - the area where the plant’s leaves and buds develop - is crucial. 

Measuring the temperature here gives you a direct insight into the environment your plants are experiencing. It’s all about maintaining a balance that encourages healthy leaf and bud development without causing heat stress.

Place your sensor at the same height as the top of your plants directly under your lights. It’s crucial that you adjust the height of your sensor as your plants grow otherwise your data won’t show a true representation of the environment the plant is experiencing. 

If you forget to move your sensor up as your plants grow the top of your plants will be a lot hotter than you want which will damage trichrome and terpene production later in flower. This is a common issue with many growers and can reduce the quality of your final results.

An illustration explaining that a grow sensor should be moved up as the plant grows.

Adjusting the sensor height can be difficult depending on the size of your room and plant density but there are some simple solutions that can make this easy!

  1. Place your sensor on some long nylon string, loop the string through your grow tent or grow ceiling and tie the string to something you can access easily. As your plants grow you can then pull the string to move the sensor up. This makes sensor placement a breese! 
  2. Place your sensor on a tripod. As your plants grow, adjust the height of your tripod. This is great if you're growing in a larger space or can’t easily hang a sensor directly under your light. 

Try to avoid hanging your sensor at the edge of a tent or grow room or not below a grow light. The environment at the edges of your space will most likely be cooler, the same applies for areas that aren't receiving direct grow light.

An illustration explaining that the grow sensor should not be placed away from the light.

Try your best to place your sensor under your light. Most lights give of enough heat to affect the temperature around your plant. If your sensor isn't in the same lit environment you won’t have a true understanding of how hot the environment is below your light source.

An illustration showing where to place a grow sensor under a light.

Root zone

The roots are the hidden heroes, especially for plants with extensive root systems. While often overlooked, the root zone temperature can significantly influence nutrient uptake and overall plant health. 

Cooler temperatures here can slow down growth, while too much warmth can lead to root rot and other issues. A consistent, slightly cool to warm temperature in the root zone is key for healthy growth.

Ambient air

The general air temperature around your plants matters too. This includes different spots in the grow area, such as near the lights, walls, and airflow paths. 

Because plants are sensitive to temperature fluctuations, maintaining a consistent ambient temperature helps ensure all parts of the plant are in an ideal growing environment.

By focusing on measuring temperature in these three key areas, you can create an optimal thermal environment for your plants. This is particularly important for plants like cannabis, where precision in temperature control can make all the difference in yield and quality.

How many temperature sensors are too many for my space? 

This really depends on your goals and the size of your operation, but the more data you can uncover about your space the more you can do to fine tune your grow environment. 

If you're new to growing you should start with measuring temperature at canopy level, so one sensor. This will give a solid starting point to growing healthy plants.

Theres a good chance you’ll have multiple sensors in the equipment you buy, for example you might buy heating controller that shows you the temperature as well as buying a digital hydrometer that does the same. Buy the most accurate sensor you can afford and trust this sensor.

If you are an intermediate grower measuring the temperature at the bottom of the grow tent to help you dial in your root zone temp will take you to the next level.  

If your an advanced grower you have lots of options to fill in the blanks in your data set:

  • Place temperature sensors in your root zone using a soil probe. This will show you what's happening directly in your pot which is super useful.

  • Place probes in multiple areas and at the edges of your tent to uncover hot or cold spots in your overall canopy. Let’s say you have a 5x5 space you could place 1 sensor at the edge and 1 in the middle.

  • Place a sensor outside your tent to learn more about the difference in temperatures which can be useful if it's cold outside your tent or room but warm inside. As this is a perfect storm for causing condensation on the walls of a thin uninsulated grow tent which could cause rot.

  • Place a sensor outside, and by that I mean like, outside your house. This could help you understand your own microclimate, which could be useful if you want to use it to aid you in growing indoors.

  • Place a sensor in your water reservoir to make sure you're not providing your plants with too cold or hot water. 

An image of a digital hydrometer under a cannabis plant.

Tools for measuring temperature

In a grow room, particularly when nurturing plants like cannabis, precise temperature monitoring is vital. Various tools are available, each with its own advantages and limitations:

Digital thermometers

These are the most common and accessible tools for temperature measurement. They are easy to use and provide quick readings. However, they don’t provide the detailed data needed to take your indoor grow to the next level.

Infrared thermometers

These devices allow you to measure temperature from a distance, which is useful for hard-to-reach areas. They are great for spot-checking but might not be as accurate for ambient temperature readings.

Specialist grow room sensors: 

Smart sensors offer comprehensive monitoring, providing data on temperature, humidity, and other environmental factors. You can also connect your smartphone for real-time alerts and remote monitoring. 

This is particularly beneficial when growing indoors, as it requires a stable and controlled environment. The Grow Sensor allows you to keep a constant eye on your grow room conditions, offering several benefits:

24/7 monitoring

The Grow Sensor keeps track of your grow room around the clock, providing insights to quickly act on any changes. This constant vigilance is crucial for maintaining the optimal environment for indoor cultivation.

Real-time alerts

Get instant updates on temperature, humidity, CO2 levels, and more directly to your phone. Get the information that you need to promptly address any environmental fluctuations that could affect plant health.

Easy integration

Ready to connect with any Wi-Fi network and simple to set up via Bluetooth. The Grow Sensor is built to integrate seamlessly into your grow room setup. 

Efficiency and savings

By providing accurate data and allowing for precise environmental control, the Grow Sensor helps reduce running costs and save electricity. This efficiency is essential for growing high-quality plants while keeping expenses in check.

The Grow Sensor is more than just a temperature monitor. It's a comprehensive solution for managing the complex environment of a grow room.

The Grow Sensor and App. Grow the best plants with this grow room montor.

Factors that affect indoor growing temperatures

Creating the perfect environment to grow the best plants indoors involves more than just setting a thermostat. Several factors can influence the temperature in your grow room:


Different types of grow lights emit varying levels of heat. For example, LED lights are cooler than HPS (High-Pressure Sodium) lights. For cannabis, which can be sensitive to heat stress, choosing the right lighting is crucial to maintain the ideal temperature.


Good air circulation is key to preventing hot spots and ensuring even temperature distribution. This is especially important in densely planted areas where plants might block airflow, leading to uneven growth.

Room size and layout

The size and design of your grow room can impact how heat is distributed. Larger rooms may require more powerful heating or cooling solutions. 

In smaller spaces, arranging plants to allow for efficient air and heat circulation is crucial.

External climate

The temperature outside your grow room can affect its internal climate. For indoor cannabis cultivation, this means adapting your temperature control strategies to the changing seasons.

By understanding and managing these factors, you can create a stable and suitable environment for your cannabis plants, helping them to thrive under optimal conditions.

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Best practices for temperature monitoring

Regular and accurate monitoring

Ensure regular checks of temperature at different points in your grow room. Use accurate and calibrated thermometers or smart sensors to track the temperature closely.

Adapt to plant growth stages

Adjust the temperature as your cannabis plants progress through different growth stages. 

Respond to environmental changes

Be aware of external weather conditions and adjust your grow room's temperature accordingly. This is particularly important for maintaining a stable environment for indoor growing.

Record and analyse data 

Keep records of temperature changes and plant growth patterns manually or by using a Grow Sensor. Analyse this data to make informed adjustments for future grow cycles. With the Grow Sensor you can see a constant history for every grow cycle which makes it super easy to optermise your space. 

Following these practices will help ensure your plants are grown in an environment with the optimal temperature for each stage of their development. This in turn leads to healthier plants and higher yields.

Troubleshooting common temperature issues

Even with the best practices in place, you might encounter temperature-related challenges in your grow room. Here's how to address some common issues:


If your grow room gets too hot, it can stress your plants, leading to wilting or burned leaves. Enhance ventilation, adjust your lighting, or use air conditioners to lower the temperature.

Cold spots

Uneven temperatures can harm plant growth. Use additional heating sources or improve room insulation to combat cold spots. Regularly moving the air in the grow room or tend using oscillating fans is a great way to stabilise your environment.

Rapid temperature fluctuations

Sudden changes in temperature can shock your plants. Try to identify and eliminate the source of these fluctuations, such as drafty windows or faulty heating systems.

High humidity with warm temperatures

This combination can create an environment prone to mould and mildew, which are detrimental to plants grown indoors. Use dehumidifiers and ensure good air circulation to tackle this issue.

By being vigilant and responsive to these common temperature issues, you can maintain a stable and healthy environment for your plants, ensuring their optimal growth and development.


Mastering the art of temperature control in a grow room is a vital aspect of cultivating thriving plants. We've explored the key areas for temperature measurement, the tools at your disposal, and the various factors affecting grow room temperature. 

Implementing best practices and troubleshooting common issues can significantly enhance your ability to provide an optimal growing environment. Remember, the goal is to create a stable, nurturing habitat that allows your plants to flourish. You can achieve a bountiful and high-quality yield with the right knowledge and tools. 

We'd love to hear from you! 

Share your experiences, challenges, or success stories in maintaining the ideal temperature for your plants. Have tips or questions? Leave a comment below. Let's cultivate a space where knowledge grows as abundantly as our plants. 


Where do you put a thermometer in a grow room?

In a grow room, it's crucial to place thermometers strategically to get accurate temperature readings. The key areas are:

Canopy level: Near the top of your plants, at the level of the uppermost leaves. This helps in monitoring the temperature that directly affects your plants.

Root zone: Near the soil or growing medium. The temperature here affects root health and nutrient uptake.

Ambient room temperature: Several thermometers placed at different spots around the room, including near the lights and ventilation systems, can ensure an even temperature distribution.

What's the best temperature for a grow room?

The ideal temperature for a grow room varies but for cannabis:

  • During the vegetative stage: A range of 22°C to 30°C (72°F to 86°F) is generally recommended.
  • During the flowering stage: Slightly cooler, around 20°C to 26°C (68°F to 80°F) is preferred to promote bud development.

    But in reality it depends on many factors, some of these are: Type of plant or strain, are you wanting to grow max yield or the best quality, are you supplementing with CO2.

Remember, consistent monitoring and adjustments are key to optimal growth and yield.

Can a grow room be too hot?

Yes, a grow room can definitely be too hot, which can be detrimental to plant health. Excessive heat can lead to a range of problems including:

  • Stress on plants, leading to wilting or drooping.
  • Increased risk of pests and diseases.
  • Reduced growth rates or stunted growth.
  • Poor quality yield, especially in flowering plants like cannabis.

It's important to monitor and regulate the temperature to ensure it stays within the ideal range for the specific plants being cultivated.

How do you control the temperature of a grow room?

To control the temperature in a grow room, you can use the following methods:

  • Ventilation: Install an effective ventilation system to circulate air and dissipate heat.
  • Air conditioning: Use an air conditioner to lower the temperature, especially in hot climates or during summer.
  • Heating systems: In cooler climates, use heaters to maintain a warm environment.
  • Humidity control: Use dehumidifiers or humidifiers to manage humidity levels, which can affect temperature.
  • Lighting: Choose grow lights that emit less heat, like LEDs, if overheating is an issue.

Regular monitoring and adjustments are key to maintaining the ideal temperature for your plants.

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Tom Starley
January 2, 2024
11 min read

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