Heat stress, upwards of 100f lately.

Hey all. It's been wicked hot here the last few days and I don't have the luxury of my AC unit which is interstate at my old place (I'm I uni accom for the next few months)


The plant took a big hit with ambient temps hitting 37c, and 39-41c (over 100f) in the tent. Is there anything I can do, or should I just ride it out and hope it gets better? It's been a relatively mild summer with 28-29c being the average so far, but the last week has been rough. It's hopefully around 32c (90f) ambient the next few days, so around 35c/95f in the tent which isn't overtly bad.


The seedlings are fine but the AK420 is looking very rough. To sum it up, should I just ride it out and hope for the best? Or is there some magic I can work to help out in these temps? The humidity has been horrid as well at around 70-75%, definately a hindrance during flower.

i've seen heat stress like this...they will be ok. It's scary but they should live just fine once temps come back to normal....as long as they don't get worse than that. You could cool down the pot/roots but it sounds like that isn't feasible at the moment.

mudballs said:

i've seen heat stress like this...they will be ok. It's scary but they should live just fine once temps come back to normal....as long as they don't get worse than that. You could cool down the pot/roots but it sounds like that isn't feasible at the moment.

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I just purchased another AC off kogan 5 mins ago, but it'll take a week or so to get here lol. I'm surprised the seedlings are taking it better than the mature plant.

The AC should arrive soon enough to give the smaller plants a chance when I throw them in 2x4 in the next few days. Begins to cool down here around late March so I should be in a better place to flower these next ones.

I do a prolonged veg during the heat of the summer, when it’s 90 degrees outside you can bet my flower tent will be 100. I made a switch to LED’s that will help me out next year.

Sadly the flowering plant will not be as good asit could have been. A few things you can do when it’s Uber hot is to open the tent while lights are on, have lights on from like 1900-0700.

You could freeze some 1gal jugs of water and place them around the pot. Wrap pot with bath towels then snug up the jugs to cool the rootzone down for hours. Or an igloo cooler and very shallow ice layer to create a better microclimate around pot.

Grojak said:

I do a prolonged veg during the heat of the summer, when it’s 90 degrees outside you can bet my flower tent will be 100. I made a switch to LED’s that will help me out next year.

Sadly the flowering plant will not be as good asit could have been. A few things you can do when it’s Uber hot is to open the tent while lights are on, have lights on from like 1900-0700.

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I was considering holding off until March like last year, but it was forecast to be a cooler summer due to la Nina and I decided to go ahead assuming i could get me AC from interstate...however I never got the AC and just hoped for the best. I'll switch the lights over to run at night (I'm currently on 16/8, turn on a 4pm and run till 10am) for the time being as it's usually 21-22c nights and hope for the best.

I saw 109f the other day and freaked lol.

Do you have the option of dimming the lights? Especially in VEG that can assist in temperature control. Last summer I had to run my Growers Choice 720 fixtures at 50% instead of 75% to lower temps. My VEG was hitting as hot as 90 °F / 32 °C.

With the hotter temps I noticed the plants enjoy a bit higher humidity, I was letting the humidity ride as high as 65% when the temps got above 82 °F / 27 °C or so..

Maybe you could install a swamp cooler if your humidity isn't too high as it is? They're usually $100-150 and its basically a mini fridge with a fan and evaporator coil. They work great in tent grows but unless you can order one off Amazon or something probably best to just vent that tent as best as possible.

calvin.m16 said:

Do you have the option of dimming the lights? Especially in VEG that can assist in temperature control. Last summer I had to run my Growers Choice 720 fixtures at 50% instead of 75% to lower temps. My VEG was hitting as hot as 90 °F / 32 °C.

With the hotter temps I noticed the plants enjoy a bit higher humidity, I was letting the humidity ride as high as 65% when the temps got above 82 °F / 27 °C or so..

Maybe you could install a swamp cooler if your humidity isn't too high as it is? They're usually $100-150 and its basically a mini fridge with a fan and evaporator coil. They work great in tent grows but unless you can order one off Amazon or something probably best to just vent that tent as best as possible.

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I'm running a 120w quantum board at 80w ATM, around 14" from the top. Dimmed it down and moved it closer a few days ago when the heatwave started. I'm getting around 500umol at the seedling level, and 900umol at the top of the plant ATM so I have room to dim and keep DLI. . If the heat keeps up i might consider dimming it a bit more.

It's not too critical as I have a few seedlings popped and enough weed to last me months already, so might just ride it out until my AC arrives and hope for the best.

VincenzioVonHook said:

I'm running a 120w quantum board at 80w ATM, around 14" from the top. Dimmed it down and moved it closer a few days ago when the heatwave started. I'm getting around 500umol at the seedling level, and 900umol at the top of the plant ATM so I have room to dim and keep DLI. . If the heat keeps up i might consider dimming it a bit more.

It's not too critical as I have a few seedlings popped and enough weed to last me months already, so might just ride it out until my AC arrives and hope for the best.

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Dang you must have some serious heat issues where the tents located. I'd just let it rip until the AC shows up and hope for the best.

I know this sounds funny but it works. Freeze a couple 2ltr pop bottles (a good few) then take out 2 and put a fan on them in the tent. It'll cool it down a bit. You need to play with the amount of bottles vs ambient temp. But it will work. You'll have to switch the bottles often and re freeze the melted ones and cycle them through. Redneck airconditioning
You can do a 2gal bucket or whatever you can work with. The bigger the block of ice the longer it'll cool for.
At least until the AC gets in. Not a permanent solution but a good temp fix
Good luck!