Aug 282015
 August 28, 2015

Marijuana plants function the best when their surroundings maintain a consistent temperature between 70 and 75 degrees Fahrenheit during the daytime, and 50 and 60 degrees Fahrenheit at night. This ideal temperature can sometimes vary, however, such as when growers add carbon dioxide to their plants, then the best temperature is right below 85 degrees Fahrenheit.

cold marijuanaCold Problems

Anything below 60 degrees Fahrenheit is going to cause problems for your marijuana plants – especially if it continues too long and if it’s during the plant’s flowering phase. This can cause problems with your resulting harvest, so it’s important to pay close attention to the temperature surrounding your plants.

With outdoors growing, you should know that they most likely will experience a night or two of as low as 50-degree temperatures. Do not fear: this should not cause long term problems for your plant and its harvest. Marijuana plants are impressively robust, but of course it is still a good idea to keep the environment within the ideal temperature range whenever possible. That being said, if the temperature gets lower than 40 degrees Fahrenheit, there will be trouble for your plant.

Make sure to download my free marijuana grow bible at this link here for more growing tips.

Cold temperatures generally cause things to slow down. Your marijuana plants won’t produce yields that are as high as normal due to the delayed growth, although you may not recognize this if it is your first season with this particular plant.

marijuana in potHow To Fix Cold Problems

When dealing with too much cold, there are some specific steps you can take to deal with its effects on marijuana plants. These methods can vary for indoor and outdoor growing areas. If you are an outdoor grower, you could give a gas patio heater a try. This is especially useful for the night when temperatures are even colder. You should aim for a consistent temperature of 60 degrees, so get as close to that as you can. Another option for outdoor growers is to cover them to provide insulation – try one made out of polyethylene plastic. If you grow in containers you can place them inside during cold nights.

If you are growing indoors, try a CO2 generator or electric heater to help balance things out. For big indoor setups, go for a hot water heater that recirculates the water throughout the garden. And make sure to download my free marijuana grow bible at this link here for more growing tips.

marijuana heat problemsHeat Problems

The cold is not the only thing that might have adverse effects on your marijuana plants – the heat can be just as troublesome. Plants that are overheating will show the earliest signs in their leaves with curling or burnt appearances.

Your plants should not have too much trouble with random bouts of heat if they are mature and have developed sizable root systems, therefore allowing them to take in more water despite the heat. If temperatures are somewhere between 80 and 90 degrees and your plants are in their vegetative state, however, you might see the development of stems that are longer and leaner than normal. Read more about the perfect temperature in the article ‘What Is The Ideal Temperature For Growing Marijuana Plants?

If you are growing your plants indoors and the grow lights are causing the temperature to be too high, then during the flowering phase, buds that are highest (or closest to the light) will be bleached and stretched out. Your plants will have burnt tips as well, but the problem with the buds is the best way to see that it’s an issue with excess heat, not light. Other signs include yellowing, brown spots, and curling leaves. Plants that aren’t receiving enough water have a higher chance of succumbing to heat stress. More tips in my free grow bible at this link here.

marijuana fanHow To Fix Heat Problems

To keep things cool indoors, you can install a ventilation fan as well as air conditioning, or else air or water-cooled lights to ensure a lower temperature despite the light intensity. Only focus on the heat that is touching your plants, since that is the only thing that will have an effect on your plants. Exhaust fans work well to dump the heat from your garden outside – just be sure to use a carbon scrubber to make sure the smell of your garden is not launched outside with the hot air.

One simple way to fix the problem is to move the light further away from the plants. Loon-watt lights are supposed to be three feet away from your plant, air-cooled lights should be between 18 and 24 inches from your plants, and water-cooled lights can be the closest: within a foot away from your plants. If you are growing outdoors and there is a heat spell, there are a number of ways to go about cooling down your marijuana plants. For instance, micro-sprayers are a good way to have significant reductions in heat – they could lower the temperature on your plants by as much as 30 degrees Fahrenheit.

Make sure to download my free marijuana grow bible at this link here for more growing tips.

If your plants are growing in containers, heat will have a more devastating effect on them. Try moving the plants out of direct sunlight to help combat excessive heat; otherwise, put them into a lighter-colored container instead because it will reflect sunlight.

To prevent heat stress from the beginning, shift your watering times to before and after the hottest part of the day – early morning and late evening, for example. This will allow your plants to absorb the water without it evaporating quickly. If need be, you can cover up your garden with a sheet in order to provide them with shade – but don’t make this a long term change, or else it will cause them to go into shock from the sun when the cover is removed.

For marijuana plants healing from heat stress, try using seaweed kelp extract to ensure that they do return to their former strength. It also serves as a preventative measure and will help keep your plants from getting heat stress again in the future.

marijuana heat cold symptomsSymptoms

The following symptoms might be displayed if your plant has heat stress:

Burnt or brown leaf edges
New, higher growth affected
Curling leaf edges
Wilting and drooping leaves
Wilting and drooping of the whole plant

If you want to start growing, download my free grow guide and order some marijuana seeds. All top quality marijuana seeds are available in my marijuana seed shop. We ship seeds to the US, CA and many other countries. For any growing related question please visit the marijuana support page.




About Robert Bergman

Robert Bergman is a master marijuana grower. Robert Bergman is the author of 'Marijuana Plant Care' and 'The Marijuana Grow Bible'.
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  10 Responses to “Temperature Problems And Marijuana Plants”


    I would like to see more delineation between indoor and sun grown. He tends to mix the two.


      Like what?

      How much electricity was used?

      Why care otherwise?

      Quality = Quality no matter the methods employed

      I would rather smoke pot than drive a hummer or put up christmass lights.

      Honestly, outdoor stuff always looks like outdoor stuff. I don’t see why people need to be told any difference. Its clear by looking at the stuff whether its in or out.


        “Beat it” officer narcoboy, you don’t know squat except to show up for
        shock value and little else. Go smoke a Shell no-pest strip.


    i have a 4by8 tent with a 8 inch exhaust fan,i have it in my basement bedroom and ii have the ducting going through the drop ceiling and into what we call a shop room the vent goes all the way to the end of room and hangs from joist and stops above door.that room is colder cause its not insulated is that ok to dump air into,also can i make a intake from that same room at a different spot on the floor i dont have filter on fan which is in tent,is this the best spot to hang fan is in tent i have nothing on the entry end.


    This photograph is an example they put for “heat stress”

    I don’t see this in “heat stress” much..Heat stress usually looks closer to excess light or excess fertilizer

    However, this photo looks exactly like the early stages of russet/broad mite.


      I’m a new grower this is my first plant I planted it June 22 and it already shows it’s a female. Now what do I do it’s outside in a pot and I can move it around if it’s to hot. But is there anything else I need to know.


    Anyone know about the heat stress during flower causing a fox-tailing in the buds and how to fix?


    Thanks for sharing the tips, I can imagine that temperature makes a huge difference, especially if you’re growing your plant indoors. Finding a good balance of temperature will make growing your plants much easier. Thanks for sharing.


    I’ve grown for quite a few years now, both indoor and outdoor ‘girls’ in a mile high location somewhere near the southern central Oregon/NoCali border. Once Fall starts they are constantly exposed to night time temperatures in the low 20’s with no discernible negative effects. In fact I’d say they even thrive on it. So, I’m always surprised when I read that weed ‘does poorly’ when exposed to temps drop ‘below 40’! I grow in the ground with very well prepared plant pit backfill and I consistently take 2-5 lbs per lady even planting as late as the middle of June and the buds are extraordinarily dense, swimming in trichome production, and sticky! I’ve grown C99, Green Crack, Velvet Kush, Blue Dream, Chemdawg, Afghani Bull Rider and a whole slew of other genetics and ALL of them did just fine in these low temps. One year I had some Jack Herer last PAST Christmas into New Years with so much snow it literally covered the plants and when I uncovered them, they had been literally flattened to the ground, but had turned a gorgeous purple and after trimming and curing was some of my most sought after product! Anyone care to chime in on this? While the cold issue may certainly be problematic during veg, from years of experience I’m just not seeing the issues with cold weather during flowering I keep reading about! So, what am I missing?

    MUCH Aloha a Ke Akua pu e pili mau na pomaika’i ‘ia ‘oe a hui hou kakou ~ ~ ~


      That’s what i wanted to hear man. I can’t chime in too much on the subject because this is my first time growing outdoors in a cold climate (Central Oregon), but I can say that I am growing three different strains right now (Fire Og, Skywalker, and Honeybucket) and all of them have been exposed to temps in the low 30s and are still looking great and the buds are fattening up more and more everyday. I am about six weeks into flowering and I am confident that my plants will continue to mature even with colder weather ahead, although I will cover them when temps get below the low thirtys just to be on the safe side.

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