Ideal humidity in greenhouse and grow rooms

The temperature and humidity relationship is ultimate, and if they are balanced, they can do wonders with any kind of crop. Humidity control is crucial for the grow room and greenhouses. Plants require optimum humidity and temperature for the best yield - humidity for seedlings and during flowering.

Humidity in Grow Room/Greenhouse

Plants are sensitive to a specified temperature, and humidity range in a grow room. If the humidity level is higher, it can be fatal for plant growth where the leaves open to fungus/pests’ attacks.

Humidity in grow rooms/greenhouses works with photosynthesis and evapotranspiration. During the daytime, photosynthesis occurs due to chlorophyll, which helps them use carbon dioxide and photons to get carbohydrates. Via this process, plants’ leaves generate water vapors into the surroundings contributing to the humidity of the air.

If, in case, you are growing crops in the grow rooms during the fall and spring seasons, you better know these are when humidity-related diseases are usually at their peak. Long sunny days increase the transpiration of moisture from leaf surfaces and evaporation from the soil. Also, the warm air will hold the moisture in the vapor form. At night, condensation occurs once the air cools to the dew point, and water droplets are formed on more excellent surfaces. Moisture promotes the germination of fungal pathogen spores such as Botrytis and powdery mildew, quickly killing plants. This fungal pathogen spreads from plant to plant, and the entire crop can destroy by them.

Healthy crops need to improve cultural practices and environmental control strategies – maintain grow room humidity. The growers should also learn the relationship between temperature and humidity to maintain the right ambiance for healthy and excellent plant growth.

The air's moisture is generally expressed as relative humidity (RH). We get the ratio between the weight of moisture in the air and the total moisture-holding capacity of a unit air volume at a specific temperature and pressure. Additionally, warm air has a higher moisture-holding capacity than cooler air; therefore, if the temperature of air increases, the relative humidity decreases even though the amount of water remains constant. Understanding this relationship is important in managing humidity in the greenhouse.

What Is The Best Humidity For Growing Cannabis Plants?

When it comes to the best humidity for weed, you better have relevant information so that you can easily make the right temperature in your greenhouse or grow room. It must be noted that Cannabis is a high-value plant, and that is why it is cultivated indoors due to its high sensitivity. Each stage of cannabis growth requires a specific temperature and humidity level to achieve optimum agrowth and high-quality yields. Humidity plays a great role in the perfect development of the cannabis plant and the proper curing of Cannabis, along with the appropriate storage of containers and conditions while in storage.

The Four Stages of Plant CycleSeedling Stage


Humidity for seedlings is different than other stages of temp and humidity for weed. 

  • Seedlings and clones like high level of humidity levels, approx 65-70%
  • Temperature with lights on 68-77 F°

If the humidity level is increased, it will allow seedlings to take water in through the leaves while their root systems are developing, and this is an optimum condition for the growth of Cannabis. 

Vegetation Period

In this stage, grow room humidity level must be lowered by 5% each week, and its range should be approx 40-70%.

Temperatures can be increased slightly if desired, and they should be with lights on 71-82 F° (lights off 8-9 F° lower). 

At this stage, roots are now more developed, and they’re able to perform most of the needed water uptake with evaporation, via which the leaves are now cooling the plants. 

Flowering Period

Very high humidity during flowering can be the worst condition for the crops. Hence, humidityy levels need to be lowered to 40-50 in this stage%. However, it is important to note that humidity shouldn’t exceed 60%.

Temperatures with lights should be 68-79 F°, and one must avoid high temperatures.

Late Flowering Period

It can be 1-2 weeks before harvesting, and during this stage, one should plan to bring down humidity levels as much as they can or to 30-40.

Temperatures with lights on 64-75 F° (lights off minus 9-18 F°) will create an ideal condition for them.

The Best Grow Room Humidity Control Solution

When growing cannabis in the grow rooms, it’s essential to avoid humidity extremes and set the best temp and humidity for weed. As humidity affects how much water and nutrients plants take in, both too little humidity and too much humidity can cause crop growing operations. However, with the right HVAC system and grow room dehumidifier, humidity can easily be managed, hence not to worry about slow crop growth, poor leaf development, and a high risk of dehydration and heat stress on your plant. Also, growers can protect their plants from mold and bud rot, poor nutrient uptake, and mildew development. If you want to know how to control humidity in a grow room, opt for one and only Altaqua Grow Room HVAC, as it will serve as an effective and efficient solution for lowering humidity levels. 


The best humidity for marijuana is important as then only one will be able to spread warm or cool dry air as needed automatically for the perfect growth of the plants. When sized correctly, dedicated commercial dehumidifiers can maintain proper indoor grow conditions every day no matter what kind of weather conditions are there. With the suggested high-end commercial dehumidification system, one can have perfect humidity in the grow room as it consistently achieves the desired room condition. Using Altaqua Grow Room HVAC will meet all your needs; hence, if you look for ideal greenhouse humidity, turn to the Altaqua Grow Room HVAC. No matter whether you require horizontal or vertical configurations and indoor or outdoor installations, get the best design, build, and integrate a dehumidification system that supports your indoor growing efforts.