28.1 atm

Any advice guys?
Its nearly time for bed, lights have been on for 1 hour 45, at 20% (very late flower) to keep temps down.
Im at 28.3c which is the same as max lights off temperature eariler.
What should I do?

61 views, no help. Not unexpected
I came here from reddit and Facebook looking for experienced help, but seem to get actual help there, even though i get 10 different answers.
10 is better than fuck all I guess

I wouldn't raise it just to create a temperature gap. In a heat wave I'd run the lights-on period as cool as you can get it and let the difference disappear for a few days. Cannabis doesn't need a warm lights-on temp plus a cooler lights-off temp to finish. It needs a leaf temp it can live with and air that isn't sitting stale around the buds.

28C-ish isn't panic by itself, especially with the light dimmed, but late flower at 62-65% RH is the part I'd be watching. Your VPD numbers are workable on paper. Dense buds don't read the app though, they sit in little still pockets. If the dehu will hold it, I'd aim more mid 50s RH than low 60s, and keep air moving through the canopy without blasting one cola all night.

So yeah, lower if possible. Don't chase higher temps for the sake of day/night difference. Keep the light at whatever power keeps the tent under control, avoid watering right before the coolest part of the cycle, and prioritize dry moving air. A short spell at 28-29C is usually less dangerous than warm damp stagnant air in very late flower.

Thanks a lot compostmike.
Just to clarify, temperature gets to 28.5c lights off, in the day time. It then got as low as 26.5c, lights off, night time.
So opposite what it should be, as in its higher lights off, but i cant do anything about that - im asleep with an industrial air con on in my bedroom.

As you know but not many people mention for some reason is that dehumidifiers produce a lot of heat.
So when people tell me to bring RH down more - its impossible.
I have a hydrone 5 on max inside my tent. That produces a lot of heat. If i put it in my lung room its usless at bring down the humidity and just produces heat.
I have a compressor dehumidifier too, but if I put that in my lung room, humidity drops slightly but heat rockets.
I have to exhaust downstairs and suck up the humid air with that dehumidifier so my house downstairs doesn't get very humid.
The lowest humidity in my tent with 4 x 5 gallon pots full of water is 60% with hydrone 5 on full blast, but 60% is really the best it can do, but only sometimes.

So basically, its mega hot and humid and any more dehumidifiers will take me way over 29/30c lights off, and probably more lights on.
Humidity here is 60 - 90% and heat is 31c outside.
Im growing in an upstairs bedroom which gets blazing hot like an oven.
After this is over (first grow), I'll never grow in summer again.

Oh, I have 3 oscillating fans, one under canopy, one half way up tent, one at top of canopy.
They do blow on buds and always have to try and avoid mold, which i think I have so far but its hard to get in the jungle in this heat and inspect every bud.

Due to smell and neighbours, these 3 - 4 days i just have to open, water quickly, wait with tent closed, then suck up runoff and measure quickly.

lockedshed said:

Thanks a lot compostmike.
Just to clarify, temperature gets to 28.5c lights off, in the day time. It then got as low as 26.5c, lights off, night time.
So opposite what it should be, as in its higher lights off, but i cant do anything about that - im asleep with an industrial air con on in my bedroom.

As you know but not many people mention for some reason is that dehumidifiers produce a lot of heat.
So when people tell me to bring RH down more - its impossible.
I have a hydrone 5 on max inside my tent. That produces a lot of heat. If i put it in my lung room its usless at bring down the humidity and just produces heat.
I have a compressor dehumidifier too, but if I put that in my lung room, humidity drops slightly but heat rockets.
I have to exhaust downstairs and suck up the humid air with that dehumidifier so my house downstairs doesn't get very humid.

So basically, its mega hot and humid and any more dehumidifiers will take me way over 29/30c lights off, and probably more lights on.
Humidity here is 60 - 90% and heat is 31c outside.
Im growing in an upstairs bedroom which gets blazing hot like an oven.
After this is over (first grow), I'll never grow in summer again.

Oh, I have 3 oscillating fans, one under canopy, one half way up tent, one at top of canopy.
They do blow on buds and always have to try and avoid mold, which i think I have so far but its hard to get in the jungle in this heat and inspect every bud.

Due to smell and neighbours, these 3 - 4 days i just have to open, water quickly, wait with tent closed, then suck up runoff and measure quickly.

Click to expand...

That inverted day/night swing isn't worth worrying about for a few days this late. It can matter more in veg or early flower if you're chasing perfect growth, but at this point I wouldn't burn the room hotter just to make the graph look normal.

You're right on the dehumidifiers. They don't remove moisture for free, they dump heat back into the space. If running another dehu pushes you into 30C+ then you can end up worse off than just holding the low 60s RH with strong exchange and moving air. I'd rather see 28-29C with air moving than 31C and a dry number on the controller.

For the next few days I'd basically run it in damage-control mode. Keep the light as low as you can tolerate, exhaust as hard as smell allows, no late heavy watering, get runoff out fast like you're doing, and keep the fans sweeping through the canopy instead of one fan drilling one wet cola all night. If you can reach in at all, open a few little gaps around the fattest tops rather than doing a big defol now.

And inspect the densest buds first when you do get in there. Mold usually starts in the thick still bits, not the pretty exposed tops. If you find one cola starting to go, cut that section out early instead of trying to nurse the whole jungle through a heat wave.

compostmike said:

That inverted day/night swing isn't worth worrying about for a few days this late. It can matter more in veg or early flower if you're chasing perfect growth, but at this point I wouldn't burn the room hotter just to make the graph look normal.

You're right on the dehumidifiers. They don't remove moisture for free, they dump heat back into the space. If running another dehu pushes you into 30C+ then you can end up worse off than just holding the low 60s RH with strong exchange and moving air. I'd rather see 28-29C with air moving than 31C and a dry number on the controller.

For the next few days I'd basically run it in damage-control mode. Keep the light as low as you can tolerate, exhaust as hard as smell allows, no late heavy watering, get runoff out fast like you're doing, and keep the fans sweeping through the canopy instead of one fan drilling one wet cola all night. If you can reach in at all, open a few little gaps around the fattest tops rather than doing a big defol now.

And inspect the densest buds first when you do get in there. Mold usually starts in the thick still bits, not the pretty exposed tops. If you find one cola starting to go, cut that section out early instead of trying to nurse the whole jungle through a heat wave.

Click to expand...

Thanks a lot.
So I'll just keep doing my damage control and hope for the best.
I won't try to up lights on temp if lights off is high.
I was meant to chop on Saturday but I think it will have to be Sunday now due to the weather.
I already have extreme fox tails from previous heat wave and people telling me to turn my fc6500 light up to 90% with buds nearly touching the light, as they could take it?!

I've learned a lot and hopefully can get a good grow in cooler months.


On a side note, when I chop on Sunday, im thinking that im going to try and cut the plants in half and hang the plants in two halves as they are, so they dont dry too fast, then dry trim.
Temperature should drop to 17 - 23c.
I am worried about humidity and keeping it at 60%, although without the 4 x 5 gallon pots full of wet coco, humidity should be lower and easier to control?

I have 4 plants, 2 of which are large and the biggest one was super cropped three times and still grown past the light ( humbolt green crack 2.0).
As this plant has super crops everywhere and the branches are sideways, it limits my drying space.
Im think of using a scrogg net up top and hanging from that, then strings/ yo yos to hang stuff lower than that, on a second lower lever.
I'll have exhaust on 1 - 2 setting and maybe 2 oscillating fans on minimum, aimed at the tent roof and floor for circulation.

The picture is a week or two old and doesn't do it justice, its a jungle in there.