Cannabis Temperature & Humidity Guide

Best Grow Room Temperature for Marijuana Plants

The best marijuana these days can be harvested in an indoor grow room under a microclimate condition. There are varieties of tools that can help you to obtain the kind of temperature needed for high-yield harvest. The temperature in the grow room can be classified into two parts.

The first part is the seedling/clone-rooting stage, and the second part is the vegetative stage, which can also involve germination. In the vegetative stage, all strains of marijuana in a grow room will thrive if the temperature is stable.

Your temperature should be around 68-83° Fahrenheit when the led light is on while it is advisable to place the temperature around 59 – 68°F when the led light is off.

Twenty-four hours of light in the grow room makes marijuana plantation more compact in the vegetative stage, but the disadvantage is there will be stale/hot air in the circulation. If you have the resources to keep the lights on for 24 hours, you should have a functional extractor fan which can discharge stale air from the room and replace it with fresh air.

marijuana growing room temperature

The Ideal Temperature for Flowering Stage

During the Flowering Stage, as soon as the white hair of the marijuana begins to appear; it is time to regulate the light regardless of the strain you have. The temperature must be set at 76-82°F during this stage, twelve hours of a dark period, and twelve hours of a light period is advised.

Learn more: Week by Week Guide to Flowering Stages

Setting up a Temperature for Growing Weed

Marijuana thrives in an indoor setting where the temperature is not too humid or dry. Most of the time, Marijuana plants share the same temperature with humans; if you feel hot or cold in your grower’s room, your marijuana plants are probably experiencing it the same way as you, depending on the climate of the grow room. The temperature should be a bit cool, so they could develop better.

Suppose your marijuana plants did not undergo photosynthesis right in your grow room. In that case, it will be difficult for your marijuana plants to grow healthy. Photosynthesis in plants is a process that is not entirely dependent on light. But factors like temperature that affect light during photosynthesis can alter the process.

Though no photosynthesis is without light, the stroma is a part of the plant where photosynthesis occurs. Fluid grana (thylakoid) are also produced in the chloroplast.

All these reactions are sped up by different kinds of enzymes that depend on temperature to operate. Marijuana loves a moderate temperature, meaning not too hot or cold. Growing marijuana under moderate temperatures will help them undergo photosynthesis quicker and better compared to marijuana in extreme temperature conditions.

Marijuana plants while growing thrive in 59 – 68°F temperatures during the day or when the light is on while at night or when the light is off, ensure the temperature of weed grow room is around 68-metric Fahrenheit.

What You Get When Temperature is too High

Based on experience, high temperature is not a threat to marijuana compared to a lower temperature. Some of them do still strive when the temperature is hot, but their growth will be stunted. 

Furthermore, when the temperature is over 86°F, then that temperature will be too hot for the plants, causing them a slow photosynthesis process.

The hotter the condition around the grower’s room, the higher the chance of plants being susceptible to pests and diseases. Some pests enjoy hot conditions; some of them are powdery mildew and spider mites.

When the condition around the marijuana plant is too hot, then the atmosphere loses more water, and you will need to water it more frequently. Apart from watering the plant regularly, marijuana plants find it difficult to take up the nutrients, which helps marijuana to proliferate.

Experienced growers understand the nutrients burn, which negatively affects foliage and roots of plants.

Also, high temperature alongside high humidity can prevent the growth of your plant, causing bud rot/mold, especially when there is limited or no air in circulation. Immediately think of a way or solution to solve high temperatures and humidity, to prevent further damage to your plants and your plant buds.

What You Get When the Temperature is Cold

Experienced growers know that cold temperature is more harmful than hot temperatures in the grow room. Most of the time, cold temperatures wither the plants and sometimes kill it. You shouldn’t plant marijuana at a temperature below 43°F, it is dangerous, and you might lose your investment.

Like marijuana growing in a tropical environment, the cold climate also slows down its growth rate, making it struggle to survive. The enzymes that speed up the photosynthesis reaction find it difficult to function optimally in a cold environment. In a cold climate, leaves (buds) and roots of marijuana plants serve as a host to molds, especially when the environment is damp.

Besides, during the flowering stage, marijuana plants thrive at night when the temperature is a bit cold around 64.4°F, this same level of warmth can give blue or purple hues; this can get you excellent buds.

The Ideal Temperature for Marijuana In the Grow Room

The best temperature to grow your marijuana in a grow room is 77°F, though this can vary depending on the involved marijuana strain.

Humidity and Temperature

There are concerns about the grow room being too humid, or at times dehydrated. Whenever the marijuana plantation is too soaked, molds thrive in this kind of condition.

Molds lurk around the corner waiting for the right timing to contaminate your plants. Those that have experienced humidity in the grow room know that it is a breeding environment for all types of marijuana pests, it also affects the soil and not only the leaves as many beginners think.

Humidity on your plants can be stopped by getting a hygrometer and a thermometer. The combination of these two devices will resist or prevent humidity and free your grow room from molds.

Measuring The Grow Room

For those that are not aware, hygrometer measures humidity while a thermometer measures temperature. Having these tools will help you strike a balance between the rate of moisture and the heat metric in a grow room.

Using a thermometer that has a reader directly helps in getting an accurate figure. It is inadvisable to measure temperature while you are under the light; you might get an inaccurate result if you do so because that certain spot will be more heated and will add few metrics compared to other parts of the grow room. Measure the temperature of the grow room in every foot.

Learn more: Setting Up Perfect Growing Room

How to Measure Humidity

The hydrometer is the most known and accurate device to calculate the humidity of a place. You should know that whenever there is stale/hot air in your grow room, it determines that there is more water in the atmosphere of your grow room.

Stale air contains more water compared to cold air; water in the air will reach a part of plants, simultaneously increasing the humidity in the marijuana. Most experienced growers believe that standing in the middle of the grow room is still the best method to measure the moisture of the environment.

Unlike temperature, where you need to measure it at every one foot, humidity needs to be measured once, and that should be in the center of your grow room.

Raising Grow Room Temperature

Most people often ask how to increase the temperature in the growing room; the next few lines you are about to read will share details on how you can manage this. It is an open fact that some environments are cold all year round and growers around those conditions need temperature raises.

One of the ways to increase the temperature in the room is the usage of light with high lumens or watt, HID lights are recommended because they produce more heat compared to other light. Please note, LED light is useful if you don’t need heat to be generated by light, but if you want to raise your grow room temperature, then you need HID grow light.

Another way is to use a subpar space heater; this makes the job faster than a grow light, but it is not recommendable for beginners to use it. Ensure you are around when you plug this heater because there are growers that have lost their plants, including building due to carelessness while using the subpar space heater.

Using quality heat mats is also a good option; heat mats are usually placed under each marijuana plant.

Though they help raise the environment’s temperature quickly, they produce a lot of heat within minutes, depending on the digital temperature controller you placed in each plant. Whenever you want to purchase heat mats, make sure you are buying mats with high quality because low-quality mats come with scary fire risk.

Last but not least is using insulation. Ensure that the insulation you will use should have a reflective device because it assures to raise the temperature and light intensity. Some tents help to keep the room warm/hot. Think about getting this if you want an increase in temperature.

In conclusion, to decrease the temperature in your grow room, try to create more ventilation in the grow room and use an LED light that does not generate heat.

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