Pioneering Hydroponics

Since 1976


Getting the temperature right in your grow room

Making sure your grow room is at the correct temperature is one of the first things you’ll be told to do when you begin to grow. But did you know that the temperatures you have your room at will need to be different during different stages of growth?
Did you also know that getting it right can be the difference between getting a good crop and a great crop?
Read on and we’ll tell you everything you need to know.

How does temperature affect a grow?How does temperature affect a grow?

Basically, if you get the temperature wrong in your grow room, then you’ll severely impair your plants ability to convert energy into growth. So, the wrong temperature can effectively reduce your yield.

Too much heat can reduce water levels and therefore affect the ability for your plants to use it. Whilst low temperature levels affect the plants ability to absorb nutrients and stunt growth.

What temperature should I have my grow room set to?What temperature should I have my grow room set to?

At a basic level the general feeling is that your grow room should be set to around 21oC to achieve a good crop. But if you’re looking to improve your yield and get the most from your plant at each stage of growth, you will want to amend the temperature slightly for each.

Growing from clones and seedlings will require a slightly higher temperature to achieve maximum growth. We recommend anywhere between 22–27oC at this stage.

During the vegetative and flowering stage, you’ll want to lower your temperature slightly to between 20–25oC, for best results.

At night or when it’s lights off, you need to make sure that the cooler air doesn’t allow your grow room temperature to drop too far. A maximum drop of 5oC is as far as it should go. Any further and you risk your plants ability to grow.


The weather outside can have a big impact on the temperature inside your grow room.
Unsurprisingly, if there’s a cold snap or a period of warmer weather you’ll see a fall or spike in temperatures in your grow room. It can be particularly difficult to manage warmer weather situations, especially if you’ve got HID lights running in your grow room.

The key is to try and avoid these spikes by employing techniques and utilising products to manage the temperature.

If the weather is particularly cold, then a heater is something that you should consider. An oil heater perhaps with a timer or a temperature thermostat is something that we highly recommend.  By having this you can plan for any drops in temperature and provide some heat before things become too cold.

Removing heat is a little more difficult and we recommend that you have a quality ventilation set up with adequate power capacity for your particular grow room size.

The intake and exhaust fans can draw cooler air from outside of your grow room and expel warm air out.
it’s a good idea to have an air movement fan with a thermostat, this will make the management process that bit easier as the fan can be set to increase in velocity based on your goal of achieving an ideal temperature.

For those of you that are looking for a more comprehensive way of managing grow room temperature, then an air conditioning unit can be used alongside our grow room set-up.

Whilst this will help you to control your grow room temperature, the costs can be prohibitive for a small-scale grower. But, for the enthusiast or larger scale grower, this is something that you should consider.
A cheaper option which has been employed is to have large ice packs added to a grow room, with an air movement fan. This is a low-cost method to employ but is not necessarily the most effective way of reducing grow room temperature.

Another way of reducing the temperature in your grow room is to switch to a cooler lighting set-up.
A CMH or LED will help you to achieve this as they run cooler than a HID. They are though more expensive and for some growers prohibitive.



Managing temperature is key to an improved crop and there are several ways to achieve an optimum temperature as detailed in this article.
If you are looking to get the most from your crop then keep them in mind on your next grow.