How hot is too hot for my grow tent?

[SecondTimeAround]

Weather on the east coast has been hot for October and my grow tent seems a lot hotter than I think it should be. My last “crop” was grown in the winter so too much heat wasn’t a problem. The average temp goes between 79 and 81 degrees. One plant (Sour Diesel) doesn’t look healthy - leaves look like the green is draining out of them. I read that nitrogen can help heat stressed plants so I used Knox gelatin mixed in water to boost the nitrogen. That helped the plants look good for a few days but now they look like they are struggling. I’m using 1 300W LED light, a small exhaust fan, an oscillating fan in the tent plus a small humidifier. I’m growing in coco coir and using Fox Farm nutes.

 

[600m]

What is the temperature inside the tent?

 

[D.A.A.S.69]

I would try to keep it under bout 84 or lower in veg, in the 70s in flower.

 

[Weed Pharma]

It should be mentioned that the temperature of the canopy leaves, is the important one-
You can have a room that's 90f and the canopy is 78f (measured by lazer) with healthy plants.
When we talk about temps- mostly we are indicating "best" for growth or bloom- not survival.

 

[kingfish]

Do you keep your tent closed during lights on ? If you do, don't. Only close your tent during light off. I wouldn't keep my temp. at 85 for too long.

 

[Xcardplayer]

Whats the RH levela?

 

[Beach_Town_Brit]

I'm in SoCal, it's warm here a lot, and electricity is expensive. I use a window AC set to 76 degrees and piped into my tent. My LEDs add around 10-12 degrees of heat. Mostly my tent's ambient temperature at the canopy level is around 84-86 but it can hit 88 and occasionally 90. I'm not sure it's ideal but I'm very happy with my harvests and bud. As Pharma suggests the real test is leaf temperature.

Interestingly, BlackDog LEDs did some tests around marijuana thriving under higher temps under LEDs, mid 80s leaf temp at canopy.

 

[Newf]

Adding Silica can help harden the plants against heat stress. I use ArmorSi. Just be careful with your pH. Silica can raise it quite a bit so you will need some pH down or similar.