420 Magazine Background

How hot is too hot?


New Member
I see lots of posts saying that grow room temps need to be somewhere around 78 degress and 90 degrees or more is WAY too hot and will stunt growth. Outdoor plants grow great at that temp so I was wondering why the difference between indoor and outdoor temps?


Well-Known Member
Leaf density and soil volume. The more leaves, the more fins on the cooler :) The more soil, the closer to 65 the ground temp so the roots can deliver cool water from the ground into the plant.

Nothing says you can't run 90 in a hydro setup with cool res temps and plenty of fresh air circulation. At least that's my take on it.
Last edited:


Well-Known Member
Your outdoor plants aren't doing the majority of their growing during the hot part of the day. They save it for the cooler parts of the day. Too hot is anything over 90. Trust me. Try to run 90+ in a grow room with a cool reservoir and you will end up adding tons of water to your reservoir to keep up with transpiration and if you miss a day your nutrient solution can become too concentrated and burn your plants. It's best to do it right and keep temps in check rather than take chances IMO.


New Member
Thanks for the replies. So if I live in a hot climate where temps are 95-105 in July and August, would it be best to keep the plants out of the direct sunlight in some broken shade? Would it also benefit me to plant in the ground rather than in pots so the roots stay cooler?


New Member
If you can get the plants in the ground, it will mean a lot less watering for you since they dry out pretty fast in those temps in pots. Anything you can do to preserve water in the ground will be helpful (mulch , swales, etc.). They usually are ok with the hot sun, in fact my outdoor crops, with temps about the same as yours, have done very well. My outdoor has only suffered when there hasn't been enough direct sunlight. You only need to protect them when they're very young and then it's mostly because they can dry out fast.
By the time you hit July and those temps your plants should be fairly large by then and able to take the heat. Some outdoor strains can handle it well, but watering is going to be your biggest task. If you have plenty of water, then with a little soil care, they should be ok. I just know I busted my ass watering outdoors since I had to water pretty much every day, and if you can automate that, then you should be golden.
As far as indoor, there's a good post here somewhere about the effect of high temps on your plants. There is some good and bad with it. If you can find it it has tons of valuable info.
Good luck brother.


New Member
if you are outdoors and have a few bucks. lowes has a garden hose timer and then they sell attachments to make it so you can add sprayers to the hose. maybe like 35-50 bucks but would be worth it in case you may forget once in the middle of the day.
Top Bottom