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Grow room temperature chart: the ideal climate for cannabis plants

Growing cannabis indoors is both an art and a science. To achieve a high-quality harvest, it’s essential to replicate and enhance the plant’s natural conditions. This involves controlling factors like temperature using a precise Grow room temperature chart. Did you know that a variation of just 5°C can significantly impact trichome and resin production? Below, we’ll present the best indoor temperature chart for cannabis cultivation and explain everything you need to create the perfect environment for your grow room.

The importance of temperature in indoor cultivation

Cannabis has been cultivated for thousands of years, but recent technological advancements have revolutionized its growth. Today, growers can control every aspect of the growing environment, from temperature to humidity and lighting. Temperature is a critical environmental factor that directly influences the development of cannabis plants. Proper temperature control ensures optimal growth and prevents issues like heat stress, pest infestations, or mold development.

Why does temperature affect plant development?

Temperature impacts vital processes such as photosynthesis, respiration, and nutrient absorption. When temperatures are too high, plants may suffer from dehydration and leaf burn. Conversely, if temperatures are too low, the plant’s metabolism slows down, reducing its ability to grow and flower. In summary, improper temperatures can delay growth, decrease bud production, and, in extreme cases, lead to plant death. To avoid these issues, it’s advisable to consult a Grow room temperature chart that specifies ideal ranges for each stage of the plant’s life cycle.

The relationship between temperature, humidity, and plant metabolism

Temperature and humidity are closely linked in cannabis cultivation. An overly hot environment can increase relative humidity, promoting the growth of molds like mildew or powdery mildew. On the other hand, low temperatures can reduce the plant’s ability to transpire and absorb nutrients. Maintaining a balance between temperature and humidity is essential for optimal metabolism and healthy growth.

Grow room temperature chart for each cultivation phase

Each phase of cannabis cultivation has specific temperature requirements. From germination to bud fattening, it’s crucial to adjust thermal conditions to ensure optimal development. Below, we break down the ideal temperatures for each stage and how to avoid common problems.

Ideal temperature for indoor cannabis cultivation

Germination

During this stage, maintain temperatures between 20 and 25°C (68–77°F) to promote root development and initial growth. Using a propagation kit with a lid is recommended to ensure consistent temperatures, aiding in uniform and rapid seed germination. It’s crucial to monitor temperature closely, as drastic variations can affect the success of the process.

Temperatures below 18°C (64°F) can delay or prevent germination, while those above 30°C (86°F) may damage seeds or cause dehydration.

Vegetative growth

During the day, the ideal temperature is 22–28°C (72–82°F), while at night, it should not drop below 18–20°C (64–68°F). This day-night difference simulates natural conditions and promotes vigorous growth.

Factors like lighting, ventilation, and grow space size affect thermal regulation. For instance, HPS lights generate more heat than LEDs, so it’s important to adjust ventilation based on the type of lighting used.

Flowering

Flowering is a lengthy process lasting 8 to 10 weeks, during which the plant’s needs evolve. At the beginning of flowering, the ideal temperature is 20–26°C (68–79°F). Towards the end, it’s advisable to slightly reduce it to 18–24°C (64–75°F) to enhance resin production and improve bud quality. Night temperatures should be between 16 and 22°C (61–72°F). Cooler nights during this period can intensify trichome production and enhance the terpene profile, affecting aroma, flavor, and therapeutic effects.

Avoid sudden temperature fluctuations and ensure good air circulation. Thermal stress during this phase can reduce resin production and deteriorate bud quality.

Bud fattening

When buds begin to fatten, the ideal temperature is between 18 and 24°C (64–75°F). In this final phase, slightly lowering the temperature can stimulate resin production and help buds become denser. A cooler environment also promotes the concentration of compounds like cannabinoids and terpenes, resulting in better yield and harvest quality.

For specific recommended values in each phase, consult the following Grow room temperature chart.

Factors affecting temperature in an indoor grow

Controlling temperature in an indoor grow isn’t solely dependent on the external climate. Factors like ventilation, lighting type, and even the substrate used also play a role. Understanding their effects is crucial to maintain the stable environment cannabis plants need.

  • Influence of Ventilation and Air Circulation: A good ventilation system helps distribute heat evenly and prevents hot spots. Exhaust fans and circulation fans are essential for air renewal and maintaining consistent temperatures.
  • LED vs. HPS Lighting and Thermal Impact: LED lights generate less heat than HPS, making temperature control easier in small spaces. If using HPS, ensure an efficient ventilation system to dissipate heat.
  • How Substrate and Water Affect Plant Temperature: A well-aerated substrate and proper watering help regulate root temperatures. Avoid overwatering, as it can overly cool the substrate and slow growth.
Temperature control in indoor cannabis cultivation

How to measure and control temperature in indoor cultivation

Precise temperature control is essential for successful cultivation. Achieving this requires the right tools and effective strategies. Below, we explain how to measure and maintain stable temperatures in your grow space.

Recommended thermometers and sensors

Here are some tools available to measure temperature in your indoor grow:

  • Digital Thermometers: Accurate and easy to use, ideal for small grows.
  • Thermo-Hygrometers: Useful for monitoring both temperature and humidity in the grow environment.
  • Smart Sensors: Allow real-time temperature monitoring via your smartphone, facilitating remote control.
  • Climate controllers. They automate temperature and humidity regulation, which is ideal for larger or professional crops
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How to measure and control temperature in your grow room

Accurate temperature control is essential for successful indoor cultivation. To achieve this, you need the right tools and effective strategies. Here’s how to measure and maintain a stable temperature in your grow space.

Recommended thermometers and sensors

Here are some of the tools available for measuring temperature in your grow room:

  • Digital thermometers. These are accurate and easy to use, ideal for small grow setups.
  • Thermo-hygrometers. These are very useful for controlling both temperature and humidity in the grow environment.
  • Smart sensors. These devices allow real-time temperature monitoring through your smartphone, making remote control easier.
  • Climate controllers. These automate temperature and humidity regulation, making them ideal for larger or professional grow setups.
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Strategies for maintaining a stable temperature

How do you keep the temperature in your grow room stable? Here are some effective solutions. The lights and panels used for plant growth tend to generate heat, so growers need to ensure that the environment doesn’t get too hot.

  • Use of extractors and fans. These help refresh the air and reduce heat buildup. Also, place fans strategically to promote uniform air circulation.
  • Grow room insulation. Use insulating materials like polystyrene sheets or thermal blankets to prevent heat or cold loss.
  • Use of air conditioners, climate controllers, or heaters. These are useful in extreme temperatures. Climate controllers are especially effective, as they allow you to adjust both temperature and humidity. In winter or at night, when the temperature drops too much, a low-energy heater can help prevent plant stress.
  • LED lighting with thermal regulation. Some advanced LED panels feature passive and active heat dissipation systems, helping to maintain more stable temperatures. There are also models that allow you to adjust the light spectrum and intensity, which can influence the temperature in the grow area.
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Consequences of inadequate temperature

Poor temperature management can have negative effects at every stage of the cultivation process. Here are the most common symptoms and how to fix them to avoid irreversible damage.

How to regulate temperature and humidity in your grow room

Temperature too high

If the temperature in your grow room is too high, your plants may show the following symptoms:

  • Yellow leaves
  • Burned leaf edges
  • Slow growth
  • Low-density buds

If you notice these signs, act quickly. We recommend increasing ventilation, using LED lights, installing an air conditioner, or reducing the power of HPS lights.

Temperature too low

On the other hand, when the temperature is too low, your plants may show the following symptoms:

  • Dark leaves
  • Slow growth
  • Increased susceptibility to pests
  • Small buds

When this happens, it’s best to use heaters, thermal root blankets, or increase light intensity to generate more heat.

ConditionHigh Temperatures (Too Hot)Low Temperatures (Too Cold)
Leaves– Yellowing or burnt edges.- Leaves curling upward (like a “canoe”).– Dark or purplish leaves.- Stiff and brittle leaves.- Slow or stunted growth.
Buds– Airy and loose buds.- Loss of terpenes (reduced aroma and flavor).– Small and slow-developing buds.- Lower resin production.
Roots– Dry or dehydrated roots.- Increased risk of root rot from water stress.– Cold, inactive roots.- Slow nutrient and water absorption.
Metabolism– Rapid transpiration and dehydration.- Heat stress slows growth.– Slowed metabolism.- Difficulty absorbing nutrients and performing photosynthesis.
Pests and Diseases– Higher susceptibility to mites, spider mites, and fungi (e.g., powdery mildew).– Greater risk of mold and fungi due to excess humidity.- Pests may thrive in colder environments.
Flowering Effects– Premature or uneven flowering.- Loss of potency and bud quality.– Slow or incomplete flowering.- Reduced bud and resin production.
Recommended Solution– Increase ventilation and air circulation.- Use LED lights to minimize heat.- Install air conditioning or cooling units.– Use heaters or thermal blankets.- Insulate the grow space.- Raise temperature with HPS lights.

Final tips for optimizing grow room temperature

To wrap things up, here are some practical tips to help you maintain optimal grow room temperature for your indoor cannabis cultivation:

  • Monitor constantly. Use accurate measuring tools to keep a close eye on temperature levels.
  • Adjust according to the growth stage. Adapt the temperature based on the specific needs of each phase, as outlined in our grow room temperature chart.
  • Invest in quality equipment. Fans, extractors, and climate control systems are essential for a successful grow.
  • Maintain balance. Don’t overlook relative humidity, as it’s directly linked to temperature levels.

Following the guidance in the grow room temperature chart, along with adjusting humidity and other environmental factors, is crucial for achieving a high-yield, top-quality cannabis harvest. As you’ve seen, each stage of plant growth requires specific conditions that, when provided correctly, boost yields and prevent common issues like mold or heat stress.

If you want to keep learning how to improve your grow and discover more practical tips, don’t miss the upcoming posts on our blog.

Indoor Growing Temperature FAQs

Why is temperature control more important indoors than outdoors?

Outdoors, plants benefit from breeze, rain, and natural cycles. Indoors, without these factors, poor temperature control can cause rapid stress (fungus, slow growth, or burns). Without regulation, the environment can become hostile for cannabis.

What happens if nighttime temperatures are equal to or higher than daytime during flowering?

Plants need that nighttime drop to breathe and absorb nutrients. Without it, they experience metabolic stress: buds become less dense and lose aroma (due to volatile terpenes). In extreme cases, hermaphroditism can occur.

Is it worth using a root heater in winter? In which cases?

Only crucial in hydroponics or very cold substrates (like coco). Roots work best between 68–77 °F (20–25 °C). Below 64 °F (18 °C), nutrient absorption slows down. In soil, heat from lights is usually enough.

How does temperature affect nutrient absorption?

In cold conditions (below 64 °F / 18 °C), roots struggle to absorb phosphorus and potassium. In excessive heat (above 86 °F / 30 °C), nitrogen evaporates, causing deficiencies. Ideal root zone is between 68–77 °F (20–25 °C).

Should I use different temperatures for indica and sativa strains?

Sativas, coming from tropical climates, tolerate 1–2 °C (1.8–3.6 °F) more than indicas during flowering (e.g., 79–81 °F vs. 75–77 °F). Indicas, on the other hand, prefer cooler nights (64–68 °F / 18–20 °C) to bring out colors.

Can I offset high temperature by increasing humidity?

Only to a point. The ideal temperature/humidity ratio (VPD) requires balance: at 86 °F (30 °C), you’d need 70% humidity (risk of mold). Better to lower heat with ventilation or reduce light hours.
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Erik Collado Vidal

Con más de 10 años de experiencia en la industria del cannabis, sus experiencias y aprendizaje son la base del éxito de GB The Green Brand.

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