How to Monitor and Control Humidity in Your Cannabis Grow Room

cannabis humidity

Hello friends! In my quest to ensure happy plants and happy growers, I’m going to discuss something super important for your cannabis grow room: humidity.

Keeping the right humidity levels is essential to ensure healthy and happy plants. So, let’s dive into how to monitor and control humidity for the best growing results…

Monitoring Humidity In Your Cannabis Grow Room:

humid cannabis grow tent

The first step is to monitor humidity levels in your grow room. To do that you need a hygrometer. A hygrometer will measure the humidity levels in your grow room.

There are digital and analog options, but I recommend a digital one for more accurate readings.

Proper Cannabis Humidity Levels:

Cannabis plants require different levels of humidity throughout their various growth stages. Here’s a general guideline for each phase:

  1. Seedling stage: During the seedling stage, cannabis plants need higher humidity levels to support their initial growth. Aim for a humidity range of 65-70%. This encourages strong root development and helps the seedlings absorb water through their leaves until the root system is more established.
  2. Vegetative stage: As your plants enter the vegetative phase, you can gradually reduce the humidity levels. The ideal range during this stage is 55-60%. Lowering humidity at this point promotes healthy growth, encourages the uptake of nutrients, and helps prevent mold and mildew.
  3. Flowering stage: A humidity range of 55-60% is appropriate at the beginning of the flowering stage. During the final weeks before harvest you should decrease humidity levels to 30-40%. This’ll help prevent mold, and maximizes resin production.

Controlling Humidity In Cannabis Grow Spaces:

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Below are several items to consider to ensure you have an easier time controlling the humidity in your grow area. This goes beyond the typical humidifier and dehumidifier advice.

Dehumidifiers and Humidifiers:

cannabis humidifier

Humidifiers and dehumidifiers can do the heavy lifting for your grow room, especially if you live in an area with extreme humidity conditions.

If you’re buying a humidifier or dehumidifier for your grow space, get one large enough that you don’t have to fill or empty it every 4 hours.

I have a 6-Liter humidifier that can run for a few days without needing to be refilled.

Ventilation and Air Circulation:

grow tent ventilation kit

Proper ventilation and circulation can help maintain good humidity levels. Make sure your grow room has a good exhaust system and a couple of oscillating fans to encourage airflow. This will prevent hotspots, minimize condensation, and deter mold growth.

Temperature Control:

Temperature and humidity are closely related, so maintaining a stable temperature is key for reducing fluctuations in humidity.

Try to keep your cannabis grow room between 70 and 80 degrees during the day, and between 68 to 70 at night. Up to 85 degrees is acceptable if you’re growing with CO2.

Use a portable air conditioner or heater to adjust the temperature as needed.

Remember to be careful and ensure you plug these devices into an outlet that can handle the power demand.

I’ve spoken with several growers who have trouble maintaining temperature in their grow space. I’ve written a detailed post with 9 methods to help you keep the temperature down.

Water Management:

watering cannabis

The last, but maybe the least talked about tip is to be mindful of your watering schedule.

Overwatering can lead to increased humidity. Watering your cannabis plants in the morning allows moisture to evaporate throughout the day while your grow lights are on.

You can also consider using a drip irrigation system or a self-watering planter to better manage your watering routine.

If you’re curious about the proper watering techniques, check out my post on watering cannabis plants.


My name is Nick, and I'm a home grower who spends time writing about indoor growing tools and setups. My goal is for 420ExpertGuide to be a one stop shop for indoor growers to find the information they need.