Autoflowering plants like any other regular cannabis plant love to grow in a warm, cozy temperature from 24 to 32°C (75 to 86°F). However, there are many factors that can allow marijuana to grow in slightly warmer or colder environments.

Basically, cannabis plants like to be on the warm side of the scale and that allows them to grow at their full potential and at full speed.

Also if the temperature is high the air can hold more water and that reduces the humidity, eliminating the risk of fungus and mold.

The best temperature for autoflowers

Indoors you can measure and control the temperature easier and fix any extremes much faster.

The ideal temperature for your autoflower plant should be 27 to 30°C (80 – 85°F) and you should maintain this temperature for the entirety of the plant’s life cycle.

Autoflower night temperature

If you feel that a dark period is needed to grow your autoflowers (for example, you want to grow your autoflowers using a 12/12 light cycle), the temperature during that “night” period should not drop more than 10 degrees or else it could hurt the plant which can reduce its size and also the yield.

What to do if your grow room temp is too high?

If the temperature gets too high you should upgrade your ventilation and never let the temperature surpass 35°C (95°F) or else your plant will suffer and die quickly.

If the temperature is too high then the plant can’t absorb CO2 properly and it slows down the growth a lot.

The first signs of the temperature being too high are when the plant leaves start to crumble. And if the problem is not solved then your plant could start wilting and dying.

What to do if the temperature in your grow room is too low?

Usually, temperature that is too low is not an issue for indoor growers because grow lights emit heat, and more commonly growers are faced with too high temperatures.

However, sometimes, when cannabis is grown indoors in cold climates, the heat from the LED or CFL grow lights can’t heat up the grow space to the optimal temperature of 27°C. There are even times when getting 20 to 25°C temperature is hard.

In these situations, you need to add additional heating to your grow space during the dark period (if there is one) and definitely a HID (High-Intensity Discharge) lamp that produces a good amount of heat and amazing amounts of light!

Can you grow autoflowers in high temps?

Some experienced growers say that you can grow cannabis in temperatures exceeding 33°C (91°F) but then you need to enrich the air in the growing room with additional CO2 and water your plants more often.

Many growers say that this method can yield slightly more bud than the plants that were grown the usual way without the CO2 enrichment.

Do outdoor-grown autoflowers do well in cold and hot temperatures?

In the wild, cannabis plants get as much CO2 as they need, and that way they can grow in higher temperatures. But keep in mind that this additional heat at the flowering stages of growth can reduce the THC production and the autoflowering marijuana plants won’t be so potent.

Outdoors these ruderalis plants can survive big changes in temperatures and both hot and cold extremes. And If they get a little frostbite then the THC production can be enhanced but the overall growth of the plant can be stunned.

Monitoring the temperature for autoflowers

All cannabis growers should monitor their grow room temperature with digital or analog thermometers.

The best ones are the digital thermometers that have the option to track the minimum and maximum temperature because then you can see the lowest and highest temperatures and act accordingly!

Now that you know about the best temps for growing autoflowering cannabis plants, learn about what should the ideal humidity be for autoflowers!


  1. John Sorrells on

    I was just curious why you stated to only supplement the heat in the dark period. I grow with leds so in the winter additional heat is a must.

    • I think if you have such a cold environment it would be best to get a HID light as they are more efficient (lumen/watt) than LED lights and that additional heating element also draws powers thus decreasing that LED fixtures total efficiency.
      About the heating in wile the LED’s are on you are right and at winter time it can get too cold but as I told , my opinion is that than it would be more economical to get a HID light.

      • HIDs are not more efficient than LEDs. LEDs use much less energy, and produce much less heat.

  2. My leaves are starting to curl a bit I’m not to sure why this is happing, would love some advice?? Thanks

Leave A Reply