Adjusting Your Grow Environment

As a new grower, it can be very difficult to maintain a consistent environment. And even in a stable environment, the temperature and humidity will fluctuate slightly. So it’s good to know different ways of adjusting your grow environment. Sometimes the issue can be solved by small and easy solutions, while other times it can require upgrades to equipment if the easier solutions don’t work.

Monitor Your Environment

Standard Digital Thermometer/Hygrometer

It is important to monitor your grow environment to ensure you’re providing your plants with optimal conditions. You can use a digital thermometer/hygrometer, which monitors temperature and relative humidity in the air. They can be purchased for relatively cheap at most hardware stores, Amazon or Ebay. Many grow lights on Ebay or Amazon also come with a digital thermometer/hygrometer. It can also be useful to set up more than one at different heights of your grow space.


The ideal range for temperature is:

  • Vegetative Stage: 70°-85°F/20°-30°C
  • Flowering Stage: 65°-80°F/18°-26°C
  • For either stage: Decrease temperature about 7°C/10°F for lights out

Depending on the location of your grow space, you may run into issues with temperatures that are too high or too low. If temperatures get too high, it can cause slow growth, leaf cupping and heat stress. When temperatures drop too low, it can make your plant more susceptible to certain types of mold, especially if it’s also damp. If it’s too cold, plant growth will slow down and freezing temperatures can shock and even kill plants. This is why it’s important to know different ways to lower or raise the temperature of your grow space.

Ways to Increase Temperature

  • Insulate your grow space, tent or box with a material that will hold heat
  • Add a heat mat under your plants
  • Add a small heater to your grow space
  • Get a bigger grow light to increase heat

Ways to Decrease Temperature

  • Add a fan or two to the grow area
  • Add an extraction fan to your setup
  • Increase your extraction fans speed (if you have one)
  • Open tent vents to increase intake airflow
  • Add ice cubes to your humidifier
  • If you don’t want to add humidity to the room, try a 2L bottle with frozen water and place it in front of a fan to cool
  • Water your plants with ice cubes to cool the root zone in extreme heat
  • Open the tent up completely and let it cool down
  • Check that your light height is correct and raise light if needed
  • Turn down wattage on dimmable ballast (if you have one) during the hottest hours to decrease heat considerably without effecting growth too much
  • Buy a portable/small air conditioner for your grow area


The ideal range for humidity are:

  • Vegetative Stage – 40% – 70%RH
  • Flowering Stage – 40% – 50%RH
  • End of flower – <40%RH

You will probably run into issues with both low and high humidity at some point. Obviously, you are more likely to run into low humidity in the winter and high humidity issues in the summer. This is due to the weather outdoors. If humidity is too low in the seedling stage, it can slow growth quite a bit. High humidity can invite many problems including white powdery mildew, bud rot and root rot. The chances increase if you don’t have proper ventilation or airflow.

Ways to Increase Humidity

  • Lower fan speed on extraction fan
  • Lower the temperature in the grow space
  • Add water sources (saturated sponges, wet towels, etc.)
  • Add a cool mist humidifier

Ways to Decrease Humidity

  • Turn up the fan speed on extraction fan
  • Open the tent up
  • Add a dehumidifier

Practice Makes Perfect

Just like anything else, the more you grow, the easy it will become to maintain a stable environment for your plants. I learn best from having to problem solve in the moment. Now, you have the tools for adjusting your grow environment. In our first year of growing, we had to deal with both high temperatures and low temperatures. We had issues with both low humidity and high humidity. I feel like after completing each grow, we grow too, as cultivators.