Optimal Temperature for Cannabis Seedlings: Best Conditions for Growing Weed

What is the Ideal Temperature to Grow Cannabis Plants?

Are you curious about the optimal temperatures for different stages of your cannabis plant’s growth? You’ve come to the right place!

With the growing legalization of cannabis across North America, enthusiasts are increasingly interested in cultivating their own plants. A crucial aspect of successful cannabis cultivation is temperature control. Extremes in temperature—too hot or too cold—can be detrimental to your plants. Managing the right cannabis seedling temperature in your grow room is essential for achieving a high-quality yield.

In this article, we’ll explore the ideal temperatures for various growth stages of cannabis and provide tips on how to maintain the perfect temperature during the flowering stage.

Ideal Temperatures for Cannabis Growth Stages

Seedling Stage

For cannabis seedlings, the optimal temperature range is between 74-78°F (23-26°C). Maintaining this stable environment is crucial for healthy root development and overall plant vigor.

Vegetative Stage

During the vegetative stage, cannabis plants thrive in temperatures ranging from 70-82°F (21-28°C). Consistent temperatures within this range promote robust growth and strong branch development.

Flowering Stage

As your plants transition to the flowering stage, slightly cooler temperatures are beneficial. Aim for a range of 65-80°F (18-27°C). Lower temperatures can enhance bud density and resin production, leading to higher-quality yields.

Effects of Extreme Temperatures

Too Cold

When the temperature drops too low, your plant’s metabolism slows down. This can negatively affect the growth rate and bud development. The root system may not grow or function properly, leaving your plant stunted due to inadequate nutrient uptake. Specific issues from low temperatures include:

  • Slow Growth: Plants may grow at a slower pace, developing new leaves and stems more slowly.
  • Cold Stress: Cold temperatures can cause leaf discoloration and smaller yields.

Too Hot

Excessive heat can also harm your plants. While growers often think plants love heat, too much can be damaging. High temperatures can lead to:

  • Stunted Growth: Leaves may become pale or yellow, and you might notice leaf curling.
  • Heat Stress: High temperatures can cause wilting, leaf drop, and reduced yields.
  • Foxtailing: Excessive heat during the flowering stage can result in smaller, more numerous buds, known as foxtailing. High or low temperatures can also reduce the potency of cannabis flowers by inhibiting the production of THC and other cannabinoids.

Controlling Grow Room Temperature

Reducing Heat

LED grow lights generate some heat, but there are ways to cool your grow room:

  • Dehumidifiers: Use a dehumidifier to control humidity and reduce heat.
  • Air Conditioning: Install an air conditioner to maintain optimal temperatures.
  • Heat-Tolerant Strains: Grow strains that thrive in higher temperatures.
  • Upgraded Fans: Improve airflow with a more powerful grow tent fan.
  • Dimmer Knobs: If your LED grow light has a dimmer knob, lower it to reduce heat output. Consider using lights like the Agrilumia XTRAY 1000W, which come with dimming option

Increasing Heat

If your grow room is too cold, consider the following:

  • Heat Mats: Use heat mats with thermostats during the seedling stage.
  • Better Insulation: Improve your grow room insulation to retain heat.
  • Cold-Tolerant Strains: Choose strains that can handle lower temperatures.
  • Elevate Roots: Keep plant roots elevated from cold floors.
  • Avoid Direct Hot Air: Ensure hot air isn’t blowing directly onto plants to prevent leaf burn.


Temperature control plays a crucial role in cannabis cultivation. By maintaining stable temperature ranges appropriate for each growth stage, you can prevent adverse effects on plant growth and yield. Careful monitoring and adjustment of the growing environment are key to healthy plants and high-quality buds.

If you have any questions about the ideal temperature for your grow room or would like to learn more, please leave a comment below.

FAQs about Cannabis Seedling Temperature

What is the best temperature and humidity for cannabis seedlings? 

During the seedling stage, keep the temperature between 74-78°F (23-26°C) and humidity levels around 75-85%. Refer to this post for a detailed guide: [What Is The Ideal Temperature And Humidity For Your Grow Tent?]

What is the lowest temperature for cannabis seedlings? 

Cannabis seedlings should not be exposed to temperatures below 59°F (15°C), as this can cause damage to the plants.

Is 90 degrees too hot for cannabis seedlings?

Yes, 90°F (32°C) is too hot for cannabis seedlings. They require a stable temperature range of 68-77°F (20-25°C) for healthy growth. If temperatures rise above this range, take steps to cool the growing environment.

How far should my light be from my cannabis seedlings?

For LED lights, the recommended distance from seedlings is 18-24 inches (45-60 cm) during the early growth stages. Adjust the light height as seedlings grow to maintain the appropriate distance.

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