Ideal Humidity for Growing Cannabis

Ideal Humidity for Growing Cannabis featured photo

Not everyone has a green thumb and is gifted the ability to grow and nurture plants. I know it’s frustrating to give a plant your all and still have it die on you. If you’re a cannabis grower, this is the last thing you’d want and one way to avoid this is keeping an eye on ideal humidity levels for growing cannabis.

The ideal humidity for growing cannabis is anywhere between the range of 40% to 70% RH.

The thing about cannabis and humidity levels is that it’s an ever-changing number. The ideal humidity level for cannabis growing doesn’t stay the same throughout the growing process and would change according to what stage your plant is in.

Below, we will be diving in on the ideal cannabis growing humidity level according to the plant growth stage. We will also lightly touch on how humidity relates to temperature and how to either increase or decrease humidity levels as your plant needs.

Cannabis Plant Growing Basics

Cannabis growing is a very profitable industry. Many investors and growers alike are jumping in on the train as cannabis becomes more and more popular across the country.

Whether you grow cannabis for business or are simply a home grower for your personal use, it’s important to know how to properly grow and care for cannabis to ensure maximum yield and harvesting results.

Cannabis can be grown outside, if you have the space and resources, or inside grow tents and rooms if you much prefer to do so.

It can take anywhere between four to eight months to grow cannabis. When it comes to cannabis, a lot of factors come into play, including: sunlight, soil moisture, water, temperature, and humidity. All these can affect how and when your cannabis plant grows.

How your plants grow and yield would depend on a lot of factors like where you’re growing them and the conditions of the environment it’s grown under. But one thing remains for sure: cannabis thrives well in a controlled environment.

One factor you can control and should keep an eye on when growing cannabis is humidity.

Why is Humidity Important for Growing Cannabis?

Humidity is the measure and amount of water vapor in the air and in the atmosphere.

Basically, the warmer the air is, the more moisture there is and the more humid the air is. In warm and tropical climates, people feel even warmer due to high humidity levels.

Generally, cannabis plants in late bloom need low humidity levels to grow and thrive. But when growing cuttings with smaller and incomplete root systems, cannabis would need high humidity levels instead.

When humidity is low, the cannabis plant will drink up and take in more nutrition and water. This will help them yield better results.

When humidity levels become too high, the tendency for cannabis plants is to close their stomata due to lack of water and moisture it needs to absorb. This leads to a stunt in the growth of the plants.

To further understand the relationship between humidity levels and growing cannabis, let’s briefly go over the three types of humidity:

Absolute humidity

This refers to the actual amount of water vapor in the air or atmosphere of a specific area.

Specific humidity

This refers to the ratio of the amount of water vapor in the air to the amount of dry air in a specified area.

Relative humidity

This refers to the actual amount of water vapor in an area relative to the speculated amount of water vapor that could be in that area. This is written in %RH and is what is typically referred to in weather reports. Relative humidity is generally easier to measure than the first two types.

When talking about growing plants and humidity, relative humidity (%RH) is generally used.

Ideal Humidity for Growing Cannabis

There is no one set answer to the query of ideal humidity for growing cannabis. Cannabis plants would require different humidity levels in different stages of growth.

But generally, the ideal humidity for growing cannabis ranges anywhere from 40% to 70%.

Ideal temperature for growing cannabis

Temperature is as important as humidity levels when growing cannabis plants.

Temperature has direct effects on an area’s humidity levels. The hotter the air is or the higher the temperature is, the higher the humidity level is. And in the same way, cold air is or low temperatures means there is less humidity in the area.

The ideal temperature for growing cannabis is anywhere between 62°F (17°C) to 87°F (31°C).

Too high temperatures or too low temperatures, the most likely problem you will have to deal with is very slow cannabis growth. When the growing air temperature gets too hot or too cold, the plant is prone to damage and may eventually die.

Ideal humidity for grow tent

Cannabis has long been cultivated mostly indoors due to its high sensitivity. As mentioned above, cannabis thrives and grows well inside a controlled environment.

Many growers, whether for business or personal use, tend to turn to grow tents and grow rooms.

For grow tents and grow rooms, ideal humidity levels of 40% to 70% and ideal temperature of 62°F (17°C) to 87°F (31°C) still apply.

The main advantage of growing cannabis in grow tents and grow rooms instead of outdoors is the maximum control over the environment.

Ideal Humidity Levels and Temperatures According to Plant Growth Stage

The ideal humidity level and temperature for growing cannabis would depend on the stage of growth your plant is in. There are essentially four basic stages growing plants go through:

Seedling stage

The seedling stage is where growers deal with seedlings or clones. In this stage, the plants have yet to grow stable roots to keep themselves pumped with nutrients. During this stage, the cannabis plant would need higher humidity levels.

At this stage, the ideal humidity level is 65% to 70%. Temperature levels would be ideal at 68°F  (at night) to 77°F (during the day).

Vegetative stage

In the vegetative stage, plants are starting to grow with more structure. Stronger roots and leaves are starting to develop too. In this stage, you can start gradually and slowly reducing humidity levels by 5% every week.

During the plant’s vegetative stage, the ideal humidity level is 40% to 70%. Remember not to go lower than 40% when gradually lowering the level each week. Ideal temperature levels would be 64°F to 75°F (at night) and 71°F to 82°F (during the day).

Early flowering stage

During the plant’s early flowering stage, the plant should have a strong root system. At this point as well, it would be a good idea to start lowering the room’s humidity levels. This also helps prevent molds and mildews from forming.

The ideal humidity level at this stage is 40% to 50%. Ideal temperatures are 68°F to 79°F.

Late flowering stage

While not necessary, you can adjust the plant’s humidity and temperature levels to further improve its yield, taste, flavor, and appearance.

At the late flowering stage, the ideal humidity level is 30% to 40%. Ideal temperature level is at 60°F to 68°F (at night) and 64°F to 75°F (during the day).

Humidity and Humidity Control Basics

As we’ve mentioned above, cannabis plants thrive and grow well in controlled environments like a grow tent or a grow room. Below, we have some tips on maintaining and keeping a consistent grow room or tent climate.

How to keep optimal humidity

The first thing you want to do to keep optimal humidity (and temperature) levels in your cannabis grow room or tent is by regularly measuring the current environmental conditions.

You can do this with two simple devices: a hygrometer and a thermometer.

A hygrometer is a device that can measure humidity levels in a given environment. And a thermometer is a device that can measure a space’s given temperature.

Both devices can measure the environment accurately while being relatively cheap.

Now that we’ve talked about different humidity levels and the need to reduce or increase them according to the plants’ needs, you might be wondering how you can do so.

How to increase humidity

To increase current humidity levels, try increasing the room’s temperature.

You can also try keeping the plants and soil moist to increase humidity. To do this, you can spray water on the plants and on the walls of the room.

Place some wet towels or some open containers with water strategically around the room to increase moisture level.

Lastly, use a humidifier to trap moisture in the target area.

How to reduce humidity

When growing cannabis, you want to ensure you also know how to decrease humidity levels.

First, you can do this by increasing the power of your exhaust fan to reduce the warm air inside the grow room.

You can also lower the overall temperature in the room to decrease humidity. When watering the plants, do so immediately after turning on the light before the overall room temperature rises.

And lastly, a good dehumidifier might just be your best shot at decreasing overall humidity levels.


More and more people are trying their hand at growing cannabis plants, whether it’s for a business or for their own personal enjoyment. While it may seem like an easy plant to grow and harvest, there are a few key considerations to always keep in mind.

One of these things is humidity in the growing environment. To ensure the best yield and harvest, it’s important to keep in mind the ideal humidity for growing cannabis plants which ranges anywhere from 40% to 70%. The exact humidity level you should aim for would depend on what stage the plan is in.

And that has been our guide on the ideal humidity for growing cannabis. Want to know the ideal humidity for curing cannabis as well? Check out this article as the curing process is a key step. For further questions, just hit us up from any of the links below!

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