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The Ideal Indoor Humidity Chart Fahrenheit for Optimal Cannabis Growth

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Growing cannabis indoors can pose difficulties, especially for novices in the field. Achieving success depends on elements like lighting, temperature, and humidity. Therefore, maintaining ideal indoor humidity is essential for the overall well-being and yield of the plant.

Extreme humidity levels, whether high or low, can result in issues like mold, mildew, and hindered growth. This blog article delves into the ideal indoor humidity chart in degrees Fahrenheit, offering guidance on monitoring and adjusting humidity levels to promote flourishing cannabis plants and exploring the impact on growers and their cultivation spaces.

First, it's crucial to grasp the concept of humidity and its influence on plants.

pc altaqua ideal indoor humidity chart fahrenheit The Ideal Indoor Humidity Chart Fahrenheit for Optimal Cannabis Growth

Understanding Humidity and Its Impact on Plants

Humidity refers to the amount of water vapor present in the air. Excessive moisture can lead to the development of mold, root rot, and various plant diseases, while insufficient humidity may result in curled leaves and stunted growth. Consequently, cannabis growers must closely monitor the humidity levels within their cultivation spaces.

The perfect indoor humidity level for marijuana cultivation depends on the specific growth stage of the plant. During the vegetative stage, the optimal humidity range falls between 50% and 70%. This allows plants to absorb nutrients and water from the soil without becoming overly wet or dry. On the other hand, during the flowering stage, the ideal humidity range is between 40% and 50%.

This lower humidity level helps prevent mold growth and promotes healthy bud development.

In addition to the plant's growth stage, other factors can affect ideal indoor humidity levels. These include the size and ventilation of the grow room, the type of lighting used, and the growing medium. For example, smaller grow rooms and those with poor ventilation require lower humidity to prevent mold growth. On the other hand, a grow room with high-intensity lighting generates more heat and needs higher humidity levels to cool the plants.

Understanding common humidity problems and their solutions can help you better control humidity in your cannabis grow room.

Common Humidity Problems and Its Solution

High humidity

High humidity promotes mold growth and reduces air circulation in cannabis grow rooms, leading to stagnant air that can harm plant growth. To combat this, you can opt for a dehumidifier or install an exhaust fan, which helps reduce atmospheric humidity and maintain ideal conditions.

Low Humidity Levels

Low humidity can cause dry, damaged leaves and slow the growth of cannabis plants. You can use a humidifier or mist the plant's foliage daily to correct this. Alternatively, you can increase the temperature in the grow room, generating more moisture.

Poor Air Circulation

Stagnant air causes carbon dioxide to be produced inside the grow chamber, which is critical to the health and growth of cannabis plants. Boost air circulation by setting up fans to move air throughout the space, providing your plants with a continuous supply of fresh air.

Avoiding Overwatering

Overwatering cannabis plants may lead to waterlogged soil, decreasing humidity and causing plant damage, such as leaf yellowing or root rot. To prevent this, ensure the soil is well aerated and implement appropriate drainage methods. Additionally, adjust the watering frequency based on the plant's growth stage.

Addressing Underwatering

Inadequate watering can result in cannabis plants wilting, experiencing stunted growth, and lacking nutrients, ultimately leading to reduced yields. To counter this, ensure that the plants are adequately watered and that the soil maintains the necessary moisture levels for optimal growth.

Ensuring Proper Ventilation

Sufficient ventilation is crucial for promoting healthy growth and avoiding the accumulation of harmful chemicals or mold. To guarantee proper ventilation, utilize exhaust fans and carbon filters, and install a ventilation system that continuously draws in fresh air.

Insufficient Lighting

Lighting is critical to the growth of cannabis plants. Insufficient lighting reduces humidity and temperature and slows growth. Ensure optimal plant lighting conditions using grow lights and a proper lighting schedule.

Inconsistent Temperature

Inconsistent temperatures can slow plant growth or cause wilting, reducing yields. Install a thermostat or use temperature controls to maintain precise temperature levels necessary for cannabis plants to grow.


A pest infestation can cause significant damage to your cannabis plants, resulting in stunted growth or reduced yields. However, proper humidity control prevents common pests like mites, spiders, and thrips. In addition, you can use organic pest control methods or chemical products to eliminate problems.

Soil Nutrient Imbalance

Soil nutrient imbalances can adversely affect cannabis plants, reducing yields and slowing growth. For healthy development, ensure your soil is pH balanced and regularly add organic fertilizers. Also, test your soil for mineral deficiencies and adjust accordingly.

Common humidity issues can cause significant problems for cannabis growers, affecting the growth and yield of their plants. However, you can ensure healthy growth and a good harvest by implementing the above solutions and the methods below to maintain optimal humidity levels.

Tips for Maintaining Optimal Humidity Levels

Maintaining ideal indoor humidity levels can be challenging, but there are ways to achieve it. Here are some tips to help you maintain optimal humidity levels:

1. Control the Humidity Level

Invest in a system that helps control humidity in your grow room to maintain optimal humidity levels. Dehumidifiers, humidifiers, and air conditioning units are essential tools to help manage humidity levels.

Altaqua grows room HVAC system is specially designed for cannabis cultivation. It can perfectly control the humidity and temperature of your grow room by freely switching cooling, heating, and dehumidification functions throughout the year, providing an optimal growing environment for cannabis. In addition, the EC fan motor could adjust the latent and sensible capacities according to different growing stages' load requirements.

If you want to know more, please click for more information.

2. Temperature Matters

Along with humidity, temperature also plays a crucial role in maintaining the ideal environment for cannabis growth. Keeping the temperature between 70 and 85 degrees Fahrenheit is ideal.

3. Stay Watered

Overwatering plants is one of the most common causes of high humidity. Ensure not to water your marijuana plants too often and only add water when necessary.

4. Choose the Suitable Soil

Choosing suitable soil will help ensure proper water retention and drainage, helping to control moisture levels. For example, consider drainage and aeration mixtures such as coir or perlite.

5. Use Ventilation

Proper ventilation is essential to maintain ideal humidity levels. A well-ventilated grow room will help prevent problems like mold and mildew, keeping your plants healthy and happy. In addition, installing air circulation fans and intake and exhaust fans can help remove moisture from the air while providing fresh air.

6. Control Humidity During the Harvest Phase

After a successful planting, it is critical to maintain optimal humidity levels during the harvest phase. Keep relative humidity low - such as 30-50%, for best results.

7. Regularly Check Humidity

It's crucial to watch the grow room's temperature closely. By consistently monitoring humidity levels, you can prevent them from becoming unmanageable. Since humidity levels fluctuate based on temperature, maintaining a stable temperature aids in preserving a constant relative humidity (RH). RH represents the air's moisture ratio compared to the maximum amount of water the air can hold at a specific temperature. Cannabis plants necessitate different RH ranges at various growth stages. Most strains thrive in temperatures between 20°C and 28°C. For vegetative growth, the RH should be between 40% and 70%, while for flowering, the RH should fall between 40% and 50%.

Tips: Using a Hygrometer to Measure Humidity

Cannabis cultivators can employ a hygrometer to gauge the grow room's humidity level. This instrument measures air humidity, enabling quick assessment and control of the air's moisture content. Hygrometers are affordable and user-friendly, with various types available.

(1) Analog (pointer) hygrometers are the most basic type, utilizing a mechanical mechanism to determine humidity levels. While affordable and straightforward, they tend to be less accurate than other hygrometers.

(2) Digital hygrometers employ electronic mechanisms to measure humidity levels. These devices are more accurate than their analog counterparts and come in various price ranges. In addition, they often include additional features, such as temperature readings.

(3) Wireless hygrometers are digital hygrometers that connect to a wireless network, allowing growers to monitor humidity levels remotely for added convenience. This is an excellent option for growers who can only stay indoors sometimes.

(4) Data logging hygrometers are digital hygrometers that can record and store humidity levels over some time. This is useful for growers who want to track moisture patterns over an extended period.

(5) An intelligent hygrometer is a digital one that connects to a smartphone app. This allows growers to receive real-time notifications about humidity levels and make adjustments from their phones.

(6) Infrared (IR) hygrometers use an infrared sensor to measure humidity levels. They are more accurate than analog or digital hygrometers but are also more expensive.

(7) Psychrometer hygrometers use a psychrometer to measure humidity levels. They are accurate and precise but require more calibration than other hygrometers.

(8) The hair hygrometer uses the principle that the length of hair changes with humidity to measure the humidity level. They are less accurate than other hygrometers and are not commonly used in cannabis grow rooms.

(9) Capacitive Hygrometers and Their Functionality Capacitive Hygrometers measure humidity levels by utilizing the electrical properties of materials. Although they are generally accurate and reliable, their performance may be affected by dust and other impurities.

Among the hygrometers mentioned above, digital ones stand out for their accuracy and readability. Position the moisture meter in the center of the grow room for the most precise readings.

Furthermore, ensuring that the hygrometer is calibrated correctly and provides accurate measurements is vital. To achieve this, place the hygrometer in an airtight container with a damp cloth, and let it sit for 24 hours. The RH reading in the container should be 100%. If not, adjust the hygrometer according to the instructions.

Position the hygrometer at plant height and away from any direct sources of moisture, such as humidifiers or water supplies. Check the humidity level regularly and adjust as needed to maintain the ideal range for your cannabis plants.

8. Check for Mold

High humidity in cannabis grow rooms can lead to mold. Check regularly to ensure no mold or mildew on your plants.

9. Adjust the Watering Time of the Plants

Overwatering can result in high humidity, while overwatering can result in low humidity. Therefore, finding a balance and not watering the plants too much or too little is essential.

10. Check for Leaks

Grow room leaks can significantly affect humidity levels, so checking for gaps or holes through which moisture can seep is essential. Seal any leaks to help maintain a consistent humidity level.

11. Don't Panic When Things Go Wrong

Even with the best measures, humidity levels can still go wrong. Should such a situation arise, remain calm. Focus on pinpointing and rectifying the issue at hand, such as by adjusting the watering quantity for your plants.

12. Logging

Tracking humidity and temperature levels inside your grow room can help you identify patterns and adjust accordingly. Log your readings to track progress and change your settings as needed.

13. Consult an Expert

If you need help to maintain ideal humidity levels, consulting an expert can help. Many resources are available, including online forums and local cannabis-growing communities where you can connect with experienced growers who can offer advice and support.


The ideal indoor humidity chart, measured in Fahrenheit, depends on several aspects, such as the plant's growth phase, the growing area's size and airflow, the lighting used, the selected growing medium, and the region's weather conditions. Cannabis growers must regularly monitor humidity levels with a hygrometer and adjust when necessary. Maintaining ideal humidity levels is critical to healthy plant growth, yield, and quality. With the right tools and techniques, growers can achieve optimal humidity levels and produce quality cannabis crops.


1. What is humidity and why is it important for plant growth?

Humidity refers to the content of water vapor in the air, which has a great influence on the growth of plants. Too much or too little humidity can lead to a variety of plant health problems, including mold, root rot, and stunted growth. That's why it's important for cannabis growers to closely monitor the humidity levels of their growing space.

2. What should humidity be at 72 degrees?

At 72 degrees, indoor humidity should be between 30-50%. Maintaining this range prevents condensation and mold growth.

3. What temperature should indoor humidity be?

Indoor humidity doesn't have a specific temperature, but it should be kept between 30-50% for comfort and to prevent mold growth.

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