Like any other plant, cannabis plants also require optimal temperatures for them to grow and thrive. Cannabis temperatures can be pretty demanding for indoor and outdoor growers, but the good news is that you can learn the best temperature to grow cannabis with just a few practices.
The growing temperature for cannabis plants can also change depending on the growth phase the plant is in, and figuring it out takes a lot of time. Cannabis growing temperatures are demanding as there can be several temperature-related problems that might need adjusting from time to time. Today, we will look at the best temperature to grow cannabis and the care your plants will need.
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Ideal Temperature per Growth Stage
As the plant grows and goes through several phases, its temperature requirements will change too. You need to make sure you create the best environment as per the growth stage. Here are some of the ideal temperatures for cannabis for each stage:
Seedlings and Clones
Clones are still young plants that have no root system and use transpiration to get water. Because of this, they need high levels of humidity until their roots grow in, so you will need to create the right amount of humidity for them.
The ideal temperature for these plants ranges between 68-77˚F (20-25˚C) and high humidity. This temperature is the best for them and will encourage them to form roots quickly and helps them become self-sufficient. Seedlings will also thrive in similar temperatures.
Vegetative Stage
In this stage, your plants require high humidity of 70% or more and temperatures the same as the seedling stage (68-77˚F). The humidity can get lower as the plant grows older. This could be a problem for indoor growers as they might have to make adjustments to cater to the change. Outdoor-grown plants are more flexible and can withstand temperature fluctuations.
The plants will need cooler temperatures in the dark stage; it helps encourage growth. The temperatures should not fall under 59˚F (15˚C). Your plant can make further adjustments as it matures, surviving in lower and drier temperatures even during the day.
Flowering Stage
Your plant can withstand low temperatures and low humidity when it hits the flowering stage. The temperature can range between 65-80˚F (18-26˚C) with the lower temperatures encouraging bud growth and high quality.
Lower temperatures in the second half of this stage also help the plants have a healthy trichome production, develop the best bud color, and have a more potent taste and smell. Do not let the temperatures go over 82˚F (28˚ C) as this can slow bud growth. Make sure the temperatures are lower during dark periods, leading to increased terpene content and optimizing other plant processes.
Drying and Curing
The next step after harvesting is to dry and cure the buds. This step is necessary because it determines whether your weed will be of good quality. Even if your marijuana has the best genetics, proper drying and curing are what determines the quality.
To properly dry and cure your seeds, you will need to maintain the correct temperature and humidity throughout the entire process. The proper temperatures will prevent mold formation and stop your weed from over-drying, making it easy to produce the best product.
The correct temperature for drying and curing falls at 64˚F (18˚C) and a humidity of 45%. Do not let the temperatures fluctuate much from this to get the best results possible.
This cannabis temperature chart helps summarize the correct temperatures for the different growth phases:
| Growth Phase | Temperature | Humidity |
| Seedlings and clones | 68-77˚F (20-25˚C) | High humidity (70% or higher) |
| Vegetative stage | 68-77 ˚F (20-25˚C) | 70% or higher |
| Flowering stage | 82˚F (28˚C) | Lower humidity (60% or higher) |
| Drying and curing | 64˚F (18˚C) | Low humidity (45%) |
Significance of Temperature to Cannabis Growth
You might be asking yourself why it is so important to maintain the cannabis temperature. What happens when the temperatures fall too low? What if it is too hot? Different things can happen when the temperature drops below the ideal temperature for cannabis plants.
Cold Temperatures
Too low or colder temperatures slow down growth. If the temperatures in your grow room fall lower than 60˚F (15˚C) for an extended period, it can upset plant growth, and temperatures even lower than this can shock or kill the plant.
Some plants will still grow even under these temperatures and not show any signs of stress. These plants will, however, give a lower yield, and in some cases, the plant will not flower at all. Another effect of colder temperatures is that they can encourage the growth of mold.
Damp and cool conditions can create a breeding ground for mold that can attack your plants. Mold can also form when the frost melts, and the liquid gets over the plants. Colder temperatures and fluctuations can also lead to over-purpling of the leaves and reduce photosynthesis.
Plants exposed to colder temperatures do not grow as well or as fast as plants in optimal environments. Indoor-grownbecause plants are even more susceptible to lower temperatures. For example, a plant can start drooping after a night in low temperatures.
Hot Temperatures
Same as the lower temperatures, when cannabis plants are exposed to too hot temperatures, they will grow more slowly. This happens when temperatures go above 81˚F (26˚C) in the flowering stage. It results in airy and loose buds, and the bud growth will slow down, meaning it will take even longer to get the plant to flower and result in lower yields.
Other problems that the plant is exposed to with high temperatures include white powdery mildew, nutrient burn, spider mites, root rot, wilting from root oxygen deprivation, too much stretching, and a reduction in the aroma of the buds.
Some cannabis plants can thrive in higher temperatures up to 85˚F (30˚C), especially with bright glow lights. They can thrive even without CO2 enrichment, provided there is low humidity. Other plants can survive in even higher temperatures up to 95˚F (35˚C) in low humidity, super-bright glow lights, and high CO2 levels.
Although these plants will thrive, they might not result in a high-quality bud. Pay close attention to the bud development if growing in higher temperatures to make sure that the bud production is not limited and is not of low quality.
How to Create the Perfect Environment
No matter where you grow your plant and what medium of growth you use, you need to be concerned about the environment, with the temperature being at the front of your mind. You want to create the best temperature to grow cannabis for the plants to thrive and give a good yield.
Outdoor Growing
Outdoor growing is mainly dependent on the weather and keeping the plants warm, especially during the colder months, can be challenging. However, most outdoor strains–like Blue Dream or Do-Si-Do can endure lower outdoor temperatures, even those falling as low as 50˚F (10˚C).
This is not ideal for cannabis growth as it can negatively impact photosynthesis and slow tissue growth down. Anything falling under 40˚F (4˚C) can damage the tissue and make the plants grow slower, with some not reaching maturity on time.
Some of the ways you can keep your plants warm on colder days include:
- Using gas patio heaters
- Polyethylene plastic covering
These two methods help heat the plants, keeping them warm on cold nights. Covering them also protects them from being affected by other harmful weather elements. You want to maintain the temperature at 60 degrees for optimal plant growth.
Indoor Growing
You, as the grower, have even more control over the indoor temperatures, which means the success or failure of your plants ultimately depends on you. You need to create the correct temperature for your plants to thrive.
The problem is that the cannabis growing temperature also depends on other factors, such as where you grow the plants. The size of the room, the number of lights, airflow, and extraction rates are some of the factors that you need to consider when building a grow room.
The ideal temperature when the light is on should range between 68-77˚F (20-25˚C). The plants evaporate more the older they grow, at which the temperature can increase to 82˚F (28˚C). The temperatures should not go beyond this as it could negatively affect the plant.
With the lights off, the temperatures should range between 59-72˚F (15-22˚C). You will also need to ensure that the day and night temperatures do not have a big difference, with the maximum difference being 18˚F (10˚C).
Humidity
Another factor that you need to think of when creating a grow room is the room’s humidity. Humidity refers to the amount of water vapor available in the air. The air that the plants breathe in contains water vapor, making humidity an essential factor to cater for.
The humidity in a grow room is usually higher due to the fact that the leaves evaporate water. Out of all the water that marijuana plants absorb, they only use about 10% evaporating the remaining 90%. The air holds a certain amount of water, which means that condensation starts once the level is reached.
The temperature in your grow room plays a big role as it directly affects the amount of humidity the air holds. Colder air can handle less water vapor compared to warm air. You can use a thermometer to measure relative humidity (RH).
RH refers to the amount of moisture available in the air. Higher temperatures, for example, hold more humidity than lower temperatures; for instance, 2 pounds of 77 degrees air can contain .45 ounces of water vapor while the same amount of 68 degrees air can hold .32 ounces. Therefore, if you let air cool down, it holds less water vapor, raising relative humidity.
You want to make sure you maintain the correct level of moisture in your grow room. If you’re going to increase the level of humidity in a cold room, you can use heat from lamps, and you can turn them off to lower the levels of humidity. You need to make sure that your grow room has optimal humidity levels for your marijuana plants to grow, thrive, and give a good yield.
Adjusting Temperature and Humidity
You can use the following tools to regulate the amount of temperature and humidity in your grow room:
- Space heater. This raises the temperature and lowers humidity
- Humidifier- somewhat raises the temperature and the humidity
- Dehumidifier-raises temperature and reduces humidity
- Evaporative cooler-lowers temperatures and raises humidity
- Air conditioner- lowers temperature and humidity
Conclusion
No matter where you grow your plants, you need to ensure the cannabis temperatures are ideal for the plants. You need to create the right environment by using fans, LED lights, or polyethylene bags. Control the temperature and humidity of your growing site, and you will see your plants thriving. You can buy seeds from our marijuana seed store and get supplements and all else you will need for healthy plants.