Autoflowering plants like any other regular cannabis plant loves to grow in a warm cozy temperature form 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 at 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.

Indoors you can measure and control the temperature much easier and fix any extremes much faster. The ideal temperature for your autoflower plant should be 27 to 30 C (80 to 85F) and you should maintain this temperature for the entire plants life cycle.

If there is a dark period for your autoflower grow the temperature in the “night” should not drop more than 10 degrees or else it could hurt the plant and that would reduce its size and also the yield.

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 temperature being too high are when the plant leafs start to crumble, but if the problem is not solved then your plant could start wilting and die.

Usually too low temperature is not an issue for indoor growers because grow lights emit heat and usually growers are faced with too high temperatures, but sometimes when cannabis is grown indoors in the cold climates the heat from the LED or CFL grow lights cant heat up the grow space to the optimal temperature of 27 C. And there are times when even getting 20 to 25 C temperature is hard so in these situations you need to add additional heating to you grow space at the dark period (if there is one) and definitely a HID(High Intensity Discharge) lamp that produces good amount of heat and amazing amounts of light!

Some experienced growers say that you can grow cannabis in temperatures exceeding 33C (91 F) but then you need to enrich the air in the growing room with additional CO2 and you need to water your plants much more often. Many growers say that this method can yield you slightly more bud than the plants that were grown the usual way without the CO2 enrichment.

In the wild cannabis plants get as much CO2 as they need and that way they can grow in higher temperatures but this additional heat at the flowering stages of growth can reduce the THC production and the autoflowering marijuana 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 frost byte then The THC production can be enhanced but the overall growth of the plant can be stunned.

All cannabis growers should monitor their grow room temperature with digital or analog thermometers and the best ones are those digital thermometers that have the options of High and Low temperatures because you can see the lowest and highest temperatures and act accordingly!



  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.

    • midowo

      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.

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