Temperature and humidity play crucial roles in growing cannabis. Of course, imbalances in temperature and humidity will have adverse effects on your plants. We often pair temperature and humidity together because they are often linked – high temperatures can “hold” more water vapor than low temperatures. So, what should the temperature and humidity be throughout the various stages of growth and how can you regulate them? Let’s take a look.
Ideal Temperature and Humidity Levels
Here is a quick breakdown of a generalized needs list for your plants but be aware that each individual plant will likely have specific desires and each strain is a little bit different so watch your plants carefully for signs of stress and adjust your temperature and humidity accordingly.
| Stage of Growth | Temperature (Fahrenheit): Day | Temperature (Fahrenheit): Night | Humidity Level (Relative Humidity) |
| Seedlings/new sprouts | 77 – 79° | 69 – 72° | 80-90% |
| Clones | 74 – 78° | 69 – 72° | 75 – 85% |
| Vegetative | 71 – 82° | 64 – 72° | 60 – 70% |
| Early Flowering | 68 – 79° | 68 – 79° | 50 – 60% |
| Late Flowering | 68 – 76° | 63 – 68° | 40 – 50% |
| Drying | 65 – 74° | n/a | 50% |
How do you control temperature and humidity in a grow tent?
How to increase temperature:
- Add an electric heater
- Use heat mats
- Run your lights at night rather than during the day during winter to help keep your plants warm
- Insulate your space
How to decrease temperature:
- Add an air conditioner (and a humidifier since air conditioners dry out spaces)
- Utilize your ventilation system – increase speed/airflow
- Increase CO2, which will help cannabis endure higher temperatures
- Use LEDs rather than HID systems
How to increase humidity:
- Add a bucket of water in the tent
- Water your plants with a sprayer in addition to adding water to the soil
- Hang wet towels in your space
- Lower your fan’s speed
- Don’t use your air conditioner as much – it dries out the air
- Use a humidifier
- Add more plants
How to decrease humidity:
- Avoid overwatering
- Use a dehumidifier
- Reduce plant density – cut away excess foliage
- Reduce the number of plants in your tent
- Remove any stagnant water
- Add more fans like oscillating fans
Controlling humidity and temperature isn’t too tough! With just a few extra steps you can stabilize your environment and make a perfect home for your babies. Good luck!
