No matter what type of cannabis you are growing (photoperiod or autoflower), temperature and humidity are among the top factors for a successful grow operation. Besides them, there are also light and CO2 levels.
The temperature and humidity needs of autoflower plants are similar to the photoperiod types of cannabis, as auflowers do great in day temperatures ranging from 23 to 28 degrees Celsius and can withstand a bit colder nights, but only 5 to 10 degrees less than the daily temperature.
Since autoflowers contain a lot of the rugged Ruderalis genes in them, they are typically considered quite resistant to cold temperatures.
As for the humidity, these cannabis varieties enjoy from 40% to 60% relative humidity.
The most crucial reason you should keep temperature and humidity at optimal levels is that if they are not, this can significantly interfere with the plant’s ability to perform photosynthesis, which can substantially stunt its growth.
Too much cold (but too much heat) is never suitable for cannabis plants, and a humid environment can lead to mold or rot.
Excessive humidity can pose a significant problem during the flowering stage since buds are far more common to have issues with mold than leaves. Inexperienced growers rarely consider this issue, so it’s essential to keep this in mind.
Another thing that can lead to mold is when the grow lights are off. When we turn off the grow lights, the air becomes colder and can hold less vapor than when the lights are on, which causes dew to form on the surfaces of the plant.
Defoliating your plants is a great way to diminish mold from forming, as it prevents stale air from remaining inside the canopy of the cannabis plant.
Best Ways to Control Indoor Temperature and Humidity
The ideal way to control the temperature and humidity of your indoor grow operation is by purchasing a thermometer and a hygrometer to determine the humidity.
These devices should have remote sensors so that you can place them inside the tent and check the levels without having to open your grow tent every time.
For an accurate reading, it’s best to place them at canopy level.
How to Ventilate Properly
Adequate ventilation is crucial as it can maintain desired levels of both the temperature and humidity while at the same time giving your plants much required fresh air.
To achieve the right amount of ventilation, you need to get an extractor fan, and the better models have the option to adjust their speed.
Pricier models designed for cannabis growing also have thermometer and hygrometer sensors built into them, and such extractor fans have the option to keep the desired levels of temperature and humidity.
Optional Air Conditioning
More professional growers sometimes replace their ventilating systems with air conditioning devices.
For this to work correctly, the grow room (or tent) has to be hermetically sealed and having a source of CO2 (like a tank) is an absolute must.
As we already mentioned, this is an option generally reserved for growers with some experience under their belt.
Temperature going over optimal levels is a frequent concern for most growers, temperatures going under happen far less.
This can only occur when the grow lights are off, but since we are talking about autoflowering varieties of cannabis, this isn’t something that should concern you.
Since autoflower cannabis is typically grown with a 24/0 light schedule, the grow lights will be constantly on, and the temperature cannot get low enough for the plants to be cold.
How to Maintain Adequate Humidity
If you notice that the air is too dry, there are several simple hacks to keep an optimally humid environment.
The first is using a hand mister to spray water inside the tent, which is done by spraying the tent walls.
It’s also okay to spray the plants, but you shouldn’t do this while they are flowering, as it can lead to mold.
Wetting a towel on one side and leaving it to dry is another simple way of increasing humidity in your tent, as the water from the towel will gradually evaporate inside your tent.
Even though these methods can do the trick and keep your tent nice and humid, purchasing an electric humidifier is the best way to do it.
These devices are relatively cheap, and you don’t need a very big humidifier for a small grow operation.
Finally, if you have too much humidity, you can try mulching, covering the soil with plastic sheets to prevent the soil from evaporating too much moisture.
You also need to avoid leaving any open containers with water inside of your tent, and if the humidity is still too high, you can also buy a dehumidifier.
Autoflower Temperature and Humidity Chart
Here you have an easy-to-read chart that precisely states the optimal temperature and humidity levels for every stage of your autoflower plant.