Conditions for late flower, questions

Just me again. I’m still pretty new to growing and had started in the winter so low rh was my only real problem but with spring here I feel like I may run into some high humidity issues soon. I’m currently as high as 52% RH in late flower and one plant has some pretty fat dense buds. I have two good size fans going at least moving the air but I’m starting to wonder if that’ll be enough.
I guess my main question is what would be a good way to control the humidity inside my (39"x39") tent?
If I put my 50pint dehumidifier inside the temp jumps to at least 85 which I feel is a bit high so I wasn’t sure if a smaller one would be any better or what other options I might have?

Your best bet is to control the room the intake air is coming from.


You could try to vent the dehumidifier exhaust out the tent. It might take some duct tape and mcgyvering.
Dbrn32 has the best solution. It’s what I do.

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Yeah that was the goal originally but in order to keep the humidity down I need to run both the window ac and a 50pint dehumidifier which puts my (10’x10’) room at about 60degrees and30-35% rh, and the tent between 65-71, but still 50% rh with the lights on, or at least on these rainy days. So I’m not sure how much lower I can really get it without adding something to the tent and/or maybe even getting a bigger tent just for the air flow? Either way I may end up harvesting one of the two plants in the next few days just to be safe.

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There are a number of less invasive ways (passive) to reduce temps and lower RH.

The first is; run your exhaust fan intermittently. I have mine on a remote thermostat to maintain the peak temps in my grow space. This cuts down on the amount of air exchanges to keep your dry air in.

A physical divider between the lights and the space above the lights can be isolated and exhausted separately from the grow space. This with an exhaust fan works really well.

Run your lights at night with the dehumidifier in the space. You are only looking for a couple of degrees. I consider 85F to be my peak before I worry.

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how will shutting off my fans for any amount of time reduce humidity? But I do run my lights at night just during the day like right now its 64degrees and 53% and they’ve only been off an hr. I’m also 3 days from harvesting so I feel like 85 would be far too high. I just dont understand how I have this problem unless my tent is just too small for 2 plants but its not even they are packed in.

If the dehumidifier is in the grow space, cutting airflow through that space will allow the dehumidifier to do it’s job on the volume of air sitting in your space. The fan comes on to exchange that air and the humidity goes up. Once the temp drops the fan stops and the dehumidifier can recover the moisture. Works great because that’s what I do. In a garage. In SoCal.

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well maybe in a few months but for now Im not sure i can afford one of those. I was hoping there was somthing i could do now

A dehumidifier is well worth the investment. Happy growing :slight_smile:


A post was split to a new topic: Help with determining harvest time

i give up

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My set up is similar to this and I am in my humid ass garage as well. I keep the dehumidifier in the tent. I am not in flower yet so I keep a vent open on the bottom and one of my tower fans in front of it. When using my 6” exhaust fan it wants to pull all the dry air out so I rotate when they are on. I also run a window Ac unit with innovative duct work into the tent as well. It’s a balancing act and the more you dial it in the less effort it will take to use. I also have the RainBird temp and humidity controllers running the dehumidifier and AC unit to keep perfect harmony lol.

These things are a life/time/headache saver!

Got them off Amazon as a set.

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I’m in my last week of flower and thus is my humidity

You’ll be fine, just keep good air movement at canopy level @ThcHemplar


yeah no just my 50 pint dehum is too big for a 3x3 tent so i need to both upgrade my tent and get a smaller dehum as well as the temp controllers… on a budget of 150 a month. ill do what i can but i just dont fully trust this situation atm.


I have an oversized dehumidifier (larger than that) in a 4 X 6 X 6 enclosure and with the setpoint controller on it, the unit shuts off when it reaches RH. You might try it to give you an option for getting where you want to go. THC production can be bumped up in a low RH finish but like @TDubWilly pointed out; many growers do just fine at around 50% RH.

@dbrn32, can we get @jbum his own topic? He will get better and more answers there.


My AC basically holds my room at about 50% humidity for the entire grow.

With the tent door closed, the tents humidity basically holds 55% for the entire grow.

In the seedling stage and early veg I’ll bump humidity up to about 70% with a humidifier.

I’ve gotten my grow room where I have never have to use my big humidifier anymore. I’ll use a small dehumidifier for spot dehumidification but my tents rarely make it into the 40% range anymore

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@Myfriendis410 wait what? I was just saying my set up is similar to yours? I’m good unless I’m missing something?


Sorry; for some reason I thought there was a question there and I didn’t want to have it vanish haha. You did a better job than I did on temp/humidity management.


No worries! I tend to ramble lol

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@ThcHemplar I’ve been through many configurations in my 3 grows. I had a dehumidifier in the tent (5x5) at first. It does raise the temps. I’m in the basement, so I have a dehumidifier running down there as it is. I have that set to 50%. I have a carbon filter and fan pulling air into the tent, so it is exchanging the tent air obviously. My RH varies between 45-58%, with temps between 68°f-77°f. Tower fan, plus a few others keeping air moving. Based on my minimal experience, you’ll be fine with where you are at.

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