Ideal Grow Room Temperature

grow room temperature

Growing indoor plants require the perfect grow room temperature along with some techniques and tools. Temperature and humidity levels are necessary for plant growth and photosynthesis. The grow room temperature changes with the stages of plant life. Plants require different temperature conditions to grow. So, grow room temperature acts as the most important ingredient for indoor plantation. Let us have a look at the details about the grow room temperatures for a cannabis plant.

The best temperature for grow room varies according to the plant’s life stage. The ideal room temperature for a cannabis plant during cloning with grow lights on should be 20-25°C and with grow lights off, it should be 15-20°C. During the vegetative stage, it requires 10-15°C during the day time. You must keep the lights close in the night for cooling purposes. The ideal grow room temperature for flowering cannabis is 69-75°C with lights on and 10-15°C with lights off.

When dealing with cannabis plants you must know that they require temperature similar to cannabishumans. So, if you feel too hot or too cold in your plant area that is probably the same for your cannabis plants. If you feel that your grow room is dry or humid, that indicates you to change the grow room temperature or humidity for your cannabis plants. You have to keep checking the temperature, humidity, CO2, and several other factors to grow cannabis successfully.

Temperature and Humidity

You must consider temperature, as well as humidity for your, grow room. Humidity is known as the ratio of water vapors in the air. These water vapors can vary in your grow room. Usually, a grow room has greater humidity because of the plants’ leaves that evaporate water. For example, Marijuana plant consumes only 10% of the water from the air and evaporates the remaining 90%. Considering these conditions, you can observe that temperature and humidity affect the water vapors in the air.


You can place a heat mat under the seedling trays to provide a warm temperature. The clones must get an optimal temperature of 20-25°C. The clones must have the humidity at 65-75%RH. If you do not provide the required temperature and humidity level, your clones will dry quickly. Similarly, too much moisture can also make your seedlings rot very fast.

The Vegetative Phase

cannabisThe best grow room temperature for your cannabis plant vegetative stage is 20-30°C. You must keep the grow lights off during the night so that your plants can covert the light into energy. You must have a humid level of 45-55%RH. If your plants get too cold or too hot temperature, your plants have a risk of losing leaves production.

The Flowering Phase

During the flowering stage, you must keep the temperature low as compared to the vegetative stage. The best temperature for flowering cannabis with lights on is 68-75C. Whereas, during the night it requires 10-15°C. Both temperature and humidity must be low during the cannabis flowering stage. To prevent any issue, your humidity level must be 35-45%HV or even below this.

Drying and Curing

You must ensure that you are pulling the wet air our and fresh air keeps circulating in your grow room. If you are growing your plans in a drying room, you must maintain the temperature ranging from 66-74°F. The drying room should have 45-55% humidity for providing the desired moisture to your grow room. After 6-10 days your buds turn dry from the outside. After your plants have matured you can now cut your buds with a bud trimmer. Put them in a glass jar and place it in a cool place having a 68-72°F temperature.

Measuring Temperature

  • It is very easy to measure the temperature of your grow room. You only need to have a thermometer or a hygrometer.

    Digital Hygrometer

  • You can buy an analog or a digital thermometer from any retailer’s shop. However, digital hygrometer- thermometers are recommended.
  • These thermometers allow you to measure the minimum and maximum temperature of your grow room.
  • Moreover, you can also hang a temperature sensor on a wire to see the display outside your grow room.

What will happen if the temperature is too low?

If you turn off the grow lights for 2-3 nights it will not damage your plants. But if you continue to turn them off, your plants will get damage. You can use a heater or a CO2 generator when the lights are off.  Normally, you don’t have to increase the temperature when the lights are on. You must ensure the proper circulation of air in your room to keep the same temperature all around.

What will happen if the temperature is too high?

Excessive heat is also a problem for grow room. You cannot leave grow lights on for 24 hours. The grow lights produce enough heat that can increase your temperature to 50°C. This temperature can completely harm your plants. You can keep the temperature low by turning the lights off at night. Outside Temperature plays a significant role here as the temperature of your grow room can never be less than the outside temperature. You can correctly position grow lights and use an air conditioner to keep the temperature low.


You simply have to practice some techniques to make your plants grow. Measure the temperature daily and adjust the temperature and humidity correctly for optimal plant growth.

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