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Ideal Grow Room Cannabis Humidity And Temperature

As any seasoned cannabis grower will tell you, achieving the best cannabis humidity and temperature is crucial to the success of your crop. Getting it right means you can easily produce high-quality buds, while any mistakes can lead to a lackluster harvest or even total crop failure.

To ensure the best results, it's important to understand the impact that cannabis humidity and temperature can have on your plants.

This post will provide detailed information and practical tips on alancing temperature and humidity for cannabis. We will cover the importance of proper humidity and temperature at different plant stages and how to maintain the perfect range for healthy plants.

To help guide you through this post, we've provided a table of contents below. So it's easy to navigate and find the information you need.

Let's dive in and learn how to maintain the best humidity and temperature for your cannabis plants.

Table of Contents
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Understanding Cannabis Humidity and Temperature

Cannabis plants are sensitive to environmental changes, particularly regarding temperature and humidity. These two factors play a crucial role in your plants' overall health, growth rate, and yield.

The Relationship between Temperature and Humidity

Humidity and temperature are closely linked and significantly impact cannabis harvests.

Humidity is the amount of water vapor in the air. Warmer air can hold more water vapor than cooler air. When there is high humidity, the air can feel warmer to you and your plants. Achieving the right level of humidity, or relative humidity (RH), is essential.

  • Specific Humidity, also known as mixing ratio, is the ratio of the mass of water vapor to the mass of dry air in a sample of air.
  • Absolute Humidity is the total amount of water vapor in a specific air volume, regardless of temperature. It's typically measured in grams of water per cubic meter.
  • Relative Humidity (RH) is a percentage that shows how much water vapor is in the air compared to the maximum amount it can hold at a specific temperature. This is usually an easier value to measure. When RH reaches 100%, the air becomes saturated with water vapor, causing the dew point to be reached and water droplets to form.

Temperature is equally important as RH for cannabis growth, so controlling both is necessary for optimal yields. Remember that warmer air can hold more humidity than cooler air. So, what occurs if the growing environment becomes too hot or cold?

To better understand this, let's discuss how temperature and humidity influence cannabis growth.

How Temperature and Humidity Affect Cannabis Growth

Temperature affects the rate of photosynthesis and transpiration in cannabis plants. Photosynthesis is when plants turn light into energy. When it's too hot or cold, photosynthesis works less well. This slows the growth and can harm plants. Transpiration is when plants lose water through leaves. Higher temperatures increase it, while lower temperatures reduce it.

Humidity measures air moisture. It's important for water and nutrient uptake in cannabis plants. Plants struggle to take up water and nutrients when humidity is too high. This is because there's too much moisture in the air. When humidity is too low, plants lose water too fast. This causes dehydration and stress.

Temperature and humidity are linked through vapor pressure deficit (VPD). A balanced VPD helps plants take up water and nutrients. It also controls transpiration rates. By keeping VPD levels right, growers create good conditions for healthy cannabis growth.

Factors Affecting Cannabis Humidity

Ideal humidity for cannabis plants depends on three main factors: region, genetics, and growth stages. While other factors may also play a role, these three have the most significant impact.


Colder regions have less moisture in the air due to the temperature relationship mentioned earlier. Therefore, when growing cannabis in such areas, increasing the relative cannabis humidity to an optimal level is essential.

In contrast, hot or tropical regions generally require less cannabis humidity control. Because many cannabis plants thrive in relatively higher humidity levels.


Over time, numerous cannabis varieties have been developed. Some cannabis species are better suited to warmer, more humid environments, requiring more attention to the cannabis humidity in their grow rooms. But others are adapted to colder, less humid conditions, where managing cannabis humidity might be less of a concern.

Growth Stages

Cannabis plants require different humidity levels from germination to late flowering. In addition, each stage involves unique metabolic processes. So, the relative cannabis humidity needs will also vary accordingly, making it crucial for growers to monitor and adjust cannabis humidity throughout the entire growth cycle.

Other Environmental Factors

①Ventilation: Good airflow in the grow space helps control cannabis humidity by spreading moisture evenly and stopping humid air buildup.

②Lighting: Various grow lights produce different heat levels, affecting room cannabis humidity. For instance, HID lights create more heat than LED lights, possibly raising cannabis humidity.

③Plant Density: The number of plants in a space impacts cannabis humidity. More plants lead to higher transpiration and cannabis humidity levels.

④Watering Practices: The number of plants in a space impacts cannabis humidity. More plants lead to higher transpiration and cannabis humidity levels.

In addition to the factors mentioned above, cannabis humidity is influenced by various other elements, such as grow room design, container size, soil type, and overall cultivation techniques.

Best Humidity and Temperature for Cannabis

Next, let's explore the ideal temperature and humidity for each growth stage to ensure a thriving cultivation experience.

Seedling Stage

  • Humidity: 65-70%
  • Temperature: 68-77°F (20-25°C) with lights on / 59-68°F (15-20°C) with lights off

During the seedling stage, plants have not yet established their root systems. High humidity in the nursery helps reduce leaf water loss and lets roots grow before increasing air moisture and water loss rates.

Growers sometimes place clones and seedlings with mature plants in the same room, using plastic covers to keep moisture (and sometimes heat). This way, they can share space without affecting each other's environment. When using covers, make sure there's good airflow to avoid too much moisture and allow CO2 exchange.

Vegetation Stage

  • Humidity: 40-70%, gradually decrease in 5% increments periodically until reaching the desired humidity for transitioning to flowering (do not go below 40%)
  • Temperature: 71-82°F (22-28°C) with lights on / 64-75°F (17-23°C) with lights off

Once plants enter the vegetative stage, they gradually reduce humidity to prepare them for flowering. This allows further development of root systems and most leafy growth and stem elongation.

Start with a humidity level of 40% to 70% in the vegetative stage and incrementally reduce it to the desired humidity for the flowering stage. However, do not drop the humidity below 40% in the vegetative stage.

Flowering Stage

  • Humidity: 40-50%
  • Temperature: 68-79°F (20-26°C) with lights on / 59-70°F (15-21°C) with lights off

The optimal humidity range for cannabis flowering is 40% to 50%. Lowering relative humidity during flowering can help prevent mold and mildew.

Cooler temperatures alongside lower humidity help maintain the ideal VPD. Avoid temperatures above 79°F (26°C), particularly in the second half of flowering, as high temperatures at low humidities can quickly dehydrate plants, causing stress and negatively impacting yields.

Late Flowering Stage

  • Humidity: 35-50%
  • Temperature: 64-75°F (18-24°C) with lights on / 59-66.2°F (15-19°C) with lights off

During the late flowering stage, it's essential to maintain a slightly lower humidity range of 35% to 50%. This helps reduce the risk of mold and bud rot in the dense buds.

Let's move on to a grow room temp and humidity chart. It will help you achieve the best results.

Now you can save our infographic for reference during the growing of cannabis!

Note: These recommendations serve as a reference, as different cannabis strains may have specific requirements. During the cultivation process, it's essential to continuously monitor temperature and humidity levels and adjust accordingly.

Drying and Curing Stage

  • Humidity: 45-60%
  • Temperature: 60-72°F (15-22°C)

Now, your high-quality buds deserve expert drying and curing! This typically involves drying the buds slowly and carefully curing them. After harvesting the cannabis plant, many growers dry the buds gradually, sometimes using brown paper bags for controlled drying.

Curing the cannabis buds involves gently releasing any remaining moisture by opening the jars from time to time. This process may take a couple of months for a true connoisseur. Keep humidity levels between 45% and 60% inside the jars. About 55% humidity is ideal.

You can use humidity-regulating bags like Boveda or Integra Boost. These help keep the perfect environment inside the jars.

Perfectly cured cannabis buds are a true reward for dedicated, quality-focused growers. The buds have a strong smell and a smooth texture. They are not too dry. Best of all, perfectly cured buds offer the ultimate vaping or smoking experience. The aroma, flavor, and effects should be at their peak!

Impact of Cannabis Humidity

Like any other plant, growing cannabis requires different temperatures and humidity from seedlings to harvesting. Therefore, cannabis plants constantly need water and a different humidity level throughout every growth stage.

Managing Humidity

Providing the right humidity levels allows leaf pores to open, absorb more CO2, and grow faster. However, too much humidity can lead to diseases like bud rot due to excess moisture promoting bacterial and fungal growth on the foliage.

Benefits of Controlling Humidity Include:

  • Preventing bud rot
  • Ensuring plant survival
  • Enhancing potency
  • Improving taste

Signs of Poor Humidity Levels

Cannabis growers sometimes face issues due to poor humidity management. Here are some problems that can arise and ways to prevent them from affecting your plants.

*White Powdery Mildew

This fungal infection appears in high-humidity environments, which can be challenging since the early stages of cannabis growth require high humidity. Infected plants display white powder or mildew, but early detection can prevent further spread.

Bud Mold/Rot

This fungal infection affects the plant's dense cores (inner part), causing white or brown mold/rot. If you notice this on the plant's buds, they must be discarded as they are no longer usable.

*Nutrient Problems

While plants need nutrients to grow, too much can lead to nutrient or fertilizer burn. This results in yellow leaves with brown edges and tips. It occurs when plants absorb excessive water due to high temperatures and low humidity, which increases nutrient uptake through their roots.

*Stunted Growth

Young cannabis plants require higher humidity levels than mature ones, which thrive in lower humidity. If these needs aren't met, your cannabis plants won't achieve their full growth potential and optimal health.

How to Measure Cannabis Humidity and Temperature

Accurately measuring humidity and temperature in your grow room is essential to maintaining the ideal environment for your cannabis plants. Inaccurate measurements can lead to stunted growth, plant stress, and a lower yield.

Importance of Accurate Measurements

Humidity and temperature are closely interlinked, and even small fluctuations can significantly impact your plants.

Measuring both factors accurately is essential for optimizing plant growth and ensuring a successful harvest. Accurate measurements can also help you detect and prevent mold, pests, or nutrient deficiencies.

Tools and Equipment for Measuring Humidity and Temperature

To ensure accurate readings, you'll need to invest in the appropriate tools and equipment:

  • Hygrometer: A device used to measure relative humidity.
  • Thermometer: A tool for measuring temperature.
  • Combination devices: Some devices measure both humidity and temperature.

When placing sensors and monitors, ensure they are placed at the canopy level and away from direct airflow or light sources that could skew the readings. Regularly clean and calibrate these devices to maintain their accuracy.

Let's move on to practical tips for achieving the best cannabis humidity and temperature. Following these tips can create an ideal environment for your plants, resulting in healthy growth and a bountiful harvest.

Practical Tips for Achieving Best Cannabis Humidity and Temperature

As we aim for success in growing cannabis, having the ideal conditions is essential. So, let's dive into easy-to-follow tips for maintaining the perfect humidity and temperature, leading to healthy plants and plentiful harvests.

Climate Control

One of the key factors in achieving optimal cannabis humidity and temperature lies in effectively controlling the climate of the grow room. By maintaining a consistent environment, growers can ensure the proper balance between temperature and humidity, directly impacting the plants' overall health and growth.

Adjusting Humidity

To Increase Humidity Levels:

  • Use a humidifier
  • Place open containers of water around the grow room
  • Mist the air with a spray bottle

To Decrease Humidity Levels:

  • Invest in a dehumidifier
  • Improve airflow with oscillating fans
  • Upgrade intake fans for better air exchange

Adjusting Temperature

To Raise Temperatures:

  • Use a high-watt HPS grow light
  • Place a heat mat on the floor
  • Invest in a small space heater with a thermostat

To Lower Temperatures:

  • Increase airflow using oscillating fans
  • Run lights during the night and off during the day
  • Use a cool tube with HPS lights or switch to LEDs
  • Invest in an air conditioner

Implementing Efficient Air Circulation and Ventilation

Ensure proper air exchange by installing intake and exhaust fans, which help remove stale air and draw in the fresh air. Oscillating fans can also improve air circulation within the grow room, reducing the risk of mold, mildew, and pests while promoting stronger plant growth. Regularly inspect and clean your ventilation system to ensure optimal performance, and a healthy grow room environment.

Proper Grow Room Design and Insulation

Designing and insulating your grow room correctly can significantly impact temperature and humidity management. Consider ventilation, lighting, and reflective surfaces when designing your grow space. In addition, ensure that your grow room is well-insulated to minimize temperature fluctuations and maintain consistent conditions.

Balancing Lighting Systems and Schedules

Your choice of grow lights, and lighting schedules can greatly impact the temperature and humidity in your grow room. LED and fluorescent lights produce less heat than high-pressure sodium (HPS) or metal halide (MH) lights, which can help maintain optimal temperatures. Adjusting your lighting schedule to have lights on during cooler times of the day can also help manage temperature fluctuations.

Correct Watering Practices

Overwatering can increase humidity levels in your grow room, while underwatering can stress plants and reduce their ability to regulate transpiration effectively. Always water your plants according to their specific needs and monitor the temperature of your water and nutrient solutions to ensure optimal uptake.

Periodic Monitoring and Adjustments

It's crucial to remain proactive and adaptive, as the needs of your plants may change throughout their growth stages. Therefore, regularly monitor the temperature and humidity levels in your grow room. Additionally, check your sensors and monitors daily. Finally, make any necessary adjustments to your climate control equipment. Keep conditions within the optimal range.

Final Thoughts and Tips for a Successful Harvest

After learning about the various ways to control humidity and temperature levels in your grow room, it's important to introduce a more efficient and user-friendly solution that can simplify the process: Altaqua's grow room HVAC equipment.

Compared to the time-consuming and sometimes complicated methods mentioned above, Altaqua's grow room HVAC system offers several key advantages to effectively manage your grow room's climate:

Integrated Solution: Instead of using multiple devices and methods to regulate temperature and humidity, Altaqua's grow room HVAC system offers a comprehensive solution that can manage both factors simultaneously, saving you time and effort.

Automation and Precision: Altaqua’s grow room HVAC system is specially designed for indoor growing, considering the temperature and humidity demands at different stages. It can perfectly maintain the target humidity and temperature by heating, air conditioning, and dehumidifying all year round.

Energy Efficiency: Altaqua's grow room HVAC system is engineered for energy efficiency, which helps reduce your operational costs and contributes to a more sustainable environment.

Customization and Scalability: Altaqua's grow room HVAC equipment can be tailored to meet the specific requirements of your grow room, regardless of its size or configuration. As your operation expands, our system can easily scale up to accommodate your growing needs.


In conclusion, mastering temperature and humidity management are crucial for successful cannabis cultivation. By understanding the optimal conditions for each growth stage and implementing effective strategies to maintain these conditions, you'll be well on your way to growing healthy, high-quality cannabis plants. Regular monitoring, investing in reliable equipment, and adapting to your plants' needs are key to ensuring a thriving cannabis garden.


1. Is 60 humidity too high for flowering?

60 humidity is not necessarily too high for flowering, but it is on the higher end of the recommended range. Nearly three-fourths (73%) of respondents said the optimal humidity level in flowering rooms is 40% to 55%. Eighteen percent said 56% to 65%. While 3% of cultivators said their ideal flower-room humidity level is 76% to 80%, none said above 80% humidity was ideal.

2. How do you know if your plant has too much humidity?

When your cannabis plants are exposed to excessive moisture, they tend to sweat, just like how humans do in a sauna. You may notice that the leaves become excessively damp and stick closely together. These are signs that your plants have too much humidity, and it's time to turn it down a notch.

3. Does cannabis need humidity at night?

Yes, cannabis needs humidity at night. During the dark cycle, plants will transpire less and require higher humidity levels to prevent dehydration. The recommended humidity range for cannabis during the night cycle is 45-55%.

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