Plant Cultivation

 Best Cannabis Seedling Temperature for Growing Weed

Best Cannabis Seedling Temperature for Growing Weed

What is the Ideal Temperature to Grow Cannabis Plants?

Are you curious about the best temperatures for different stages of your plant’s growth? Well, you’ve come to the right place!

As the legalization of plants continues across North America, plant enthusiasts are increasingly interested in growing their plants. One important part of growing plants is controlling the temperature. Too hot or too cold, your plants can die either way. It may sound dramatic, but controlling cannabis seedling temperature inside your grow room is important for achieving a high-quality yield.

In the following article, we’ll take a closer look at the best temperatures for your plants and how you can achieve the ideal temp for flowering stage

Table of Contents

The Ideal Temperature for Plant Per Growth Stage

Long story short, below we’ve outlined the best temperatures for the three most important stages of weed growth. This will give you an approximate temperature guideline and help you to monitor your grow room temperatures.

  1. Seedling Stage – The best plant seedling temperatures are between 74-78°F(23-26°C).
  2. Vegetative Stage – The best plant vegetative temperatures are between 70-82°F(21-28°C).
  3. Flowering Stage – The best temperature for flowering stage is between 65-80°F(18-27°C).

What Happens When the Temperature Is Too Hot or Too Cold

On one hand, when the temperature for growing weed gets too cold, your plant’s metabolism slows down. This fall in metabolism can negatively affect the growth rate of your plant and also its buds. 

As a result, the root system won’t grow or perform as it should, which can leave your plant stunted because it’s not getting enough nutrients for healthy growth. In detail, you may find the following low-temperature damages:

  • Slow growth: Plants that are experiencing low temperatures will grow at a slower pace than usual. They may not develop new leaves or stems as quickly as they should, and their overall growth rate will be slower than normal.
  • Cold stress: Cold temperatures can cause cold stress that can further cause a series of issues such as leaf discoloration and smaller yields.

On the other hand, growers tend to think that plants love hot environments, but the truth is that too much heat could actually be hurting your plants, not helping them. If your plants are exposed to excessive heat, they are likely to meet the following situations. 

  • Stunted growth: When cannabis plants are hurt by extremely high temperatures, their leaves may become pale or yellow. You may also notice cannabis leaves curling up

yellow to brown leaves curl up

  • Heat stress: High temperatures can cause heat stress, which can lead to wilting, leaf drop, and reduced yields.
  • When your plant is exposed to excessive heat during the flowering stage, rather than concentrate on growing buds bigger, it can actually grow more buds that are much smaller, which is commonly referred to as foxtailing.

In addition to these damages, excessively high or low temperatures can also reduce the potency of cannabis flowers by inhibiting the production of THC and other cannabinoids.

How Can You Control Your Grow Room Temperature

Too Hot – The LED grow lights you use in your grow room generate a certain amount of heat. Fortunately, there are some things that you can do to lower the temperature in your grow room.

  • Use a dehumidifier inside your grow room.
  • Add an air conditioner to your grow room.
  • Try growing strains that are more conducive to additional heat.
  • Upgrade your grow tent fan to remove additional heat.

grow tent fan

  • Adjust the dimmer knob to a lower value, if there’s any. If not, consider getting one grow light that comes with a dimmer knob to precisely control the light, say, Spider Farmer SF1000

Too Cold – If your plants are grown in a way too cold environment, then the low cannabis seedling temperature can place undue stress on them and affect them through each stage of growth. Check how to increase the temperature of your grow room and make your plants more comfortable.

  • During the seedling stage, you can utilize a heat mat thermostat to raise the temperature below your seedlings.
  • Adding additional insulation can be added to your grow room. Also, consider higher-quality insulation which performs better than cheaper insulation.
  • Try growing plant strains that perform better at lower temperatures.
  • Keep the roots of the plants evaluated from the cold floor.
  • Don’t allow excessive hot air to blow onto your plant, as it can burn the leaves.


As you can see from above, temperature plays a huge role in how well your plants will grow. It's crucial to maintain stable temperature ranges within the appropriate range for each stage of cannabis growth to avoid any adverse effects on plant growth and yield. By carefully monitoring and adjusting the temperature in your cannabis growing environment, you can help ensure healthy plant growth, robust yields, and high-quality buds.

If you have any questions about the ideal temperature for your grow room or would like to learn more, then please don’t hesitate to leave a comment below. 

FAQs about cannabis seedling temperature

  • What is the best temperature and humidity for cannabis seedlings?

During the cannabis seedling stage, it’s suggested to keep the temperature between 74-78 degrees Fahrenheit and the humidity level should be around 75% - 85%. Kindly refer to this post for a more thorough understanding: What Is The Ideal Temperature And Humidity For Your Grow Tent?

  • What is the lowest temperature for cannabis seedlings?

Cannabis seedlings are sensitive to low temperatures and should not be exposed to temperatures below 15°C (59°F). Anything below that would cause damage to your weed plants. 

  • Is 90 degrees too hot for cannabis seedlings?

Yes, 90 degrees Fahrenheit (32°C) is too hot for cannabis seedlings. Cannabis seedlings require a relatively stable temperature range of around 20-25°C (68-77°F) for healthy growth. If the temperature rises above this range, you may need to take steps to cool down the growing environment. 

  • How far should my light be from my cannabis seedlings?

For LED lights, the LED light distance from seedlings is recommended to be around 18-24 inches (45-60 cm) during the early stages of growth. As the seedlings grow taller, you can gradually lower the light to maintain the appropriate distance.


About Ciki

Ciki has been navigating the digital world of SEO for over 3 years, applying her expertise originally in the software sector before turning her attention to indoor gardening. Merging her tech-savvy background with a passion for nature, Ciki offers a unique perspective on gardening, blending modern techniques with time-honored traditions.

8 thoughts on “ Best Cannabis Seedling Temperature for Growing Weed

  1. Jose Martinez says:

    the best

  2. Jose Martinez says:

    top quality!

  3. dougbream says:

    I just started utilizing heat mat for germination and seedlings, what a game changer!! My spider farmer heating mat with controller make it easy to optimize a little warmer temps in early stages. My sprouts have never taken off so quick and vigorously

  4. Jamie Bruursema says:

    Se5000 is perfect for a 3 by 3 set up seedlings only then outside considering 2 more top of the line have many different lights by far the best yep 70 to 80 degrees play with your fan speed

  5. Jamie Bruursema says:

    Se5000 is perfect for a 3 by 3 set up seedlings only then outside considering 2 more top of the line have many different lights by far the best

  6. stang1238 says:

    i try to stay between 70 and 80 F

  7. Killer Buds says:

    Frost grow all the cheapest things I could find growing up very nice and I am very proud of it not many people are Abele five foot tall veg and I got it on my frost indoor with only 500$ impressed myself I love it

  8. Ace paigey says:

    Awesome bit of information and is great to see and have something to read that is very very very helpful and useful… thanks to the gunja gods and amen

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