Reasons for a rise in grow room temperature: Improper Ventilation, Too Many Heat Producers
Not-so-Insulated Location of the Grow Tent. And how keep my grow tent cool in the summer?

Decreasing Temperature in your grow tent or room
It seems like the majority of indoor gardeners struggle with high temperature, so let’s look at ways you can decrease your temperature.
Air Conditioner
If high temperatures are wrecking your indoor garden, there is no better way to quickly bring the temperature down than an air conditioner. You can easily place them either in the marijuana grow tent or some models allow you to have them outside the tent while ducting the cool air in.
For more information on air conditioners, read our guide on choosing and sizing the best one for your growing space.
Reservoir Chillers
Many hydroponic setups keep the reservoir outside of the tent as dangerous algae can grow in the water when the temperature rises above 70 degrees. However, if you’re using a Deep Water Culture (DWC) system then this means your plants’ roots are directly sitting in the reservoir, so it will be in the tent. Reservoir chillers are crucial in DWC and other hydro setups.
Understanding Your Grow Lights
HID (HPS grow light and MH grow light)
They give you some of the best looking, highest yielding, and tastiest plants, but everyone agrees that their one big downfall is the heat they generate. If you’re using HID grow light like high pressure sodium or metal halide bulbs, you need to prepare for ways to decrease temperatures.
Air Cooled Lighting — Air-Cooled lights work by using extraction fans to pass air continuously over the lamps and then exhausting this warm air out of your grow room via aluminium ducting. If you use acoustic/insulated ducting on the outlet this will help cool your grow room even more.
LED grow light
LED has proven they’re here to stay and the best ones are reducing your grow tent’s heat by at least 40% compared to an HID of equivalent wattage. Most LED users fight will low temperatures during propagation and early veg, as LEDs have to be hung at least far from the plant’s canopy as HIDs. You can run lower wattage LEDs in your grow tent for several reasons. The biggest reason is LEDs produce light in a 120-degree angle directly hitting your canopy unlike the 360-degree angle HIDs and fluorescents which has to be redirected affecting its efficiency. The best LEDs will give you the most lumens/light for the least amount of watts, and this is why they are the “coolest” grow lights currently out there.
Hygrometers
These days all good grow rooms and indoor gardeners have hygrometers, but to get a true indication, the more the merrier. Try to have a minimum of three, one up high, one in the middle and one lower down. This will help you to identify cold spikes or heat pockets etc
Good Inner Grow Room Circulation
Some growers prefer lots of little clip fans some like stand fans others have wall mounting or floor fans. Again the more the merrier but diversity is key. For example try to alternate different fans blowing alternately as the wind outside never blows the same way for too long. Fans with oscillation or fans that have a circulating and moving louvre are ideal. If possible try to create a vortex of sort by having a fan in each corner, each one face the other helping to create a circulating vacuum of air.
Keep Humidity Under Control
Another strong catalyst behind your grow room’s temperature is a low level of humidity. As you know, low humidity causes a rise in temperature. And vice versa.
To beat with a high temperature, increase the relative humidity of the grow space. That will help plants to do exhale water vapor through leaves, resulting in coolness.