How To Manage A Grow Room That Is Way Too Cold

Last Updated on April 20, 2022 by Gary Stephen

Temperature is critical in every cultivar’s growth. If your grow room is way too cold or too hot, it can lead to plant death. Hence, we must enforce the necessary measures to provide our crop with the most suitable condition to thrive.

During the winter season, keeping the grow room warm enough can be quite a challenge. The dropping of the temperature outdoors is beyond our control. Besides, there are various ways we can manage indoor temperature. Thus, to remain within a comfortable range.

In this article, we will tap into the different techniques we can use. This is to ensure appropriate levels of temperature maintenance throughout the grow room.

Ideal Room Temperature for Plants

Before proceeding with the abnormalities, let us discuss first the basics. So, what is actually considered the normal temperature for plants?

Over and over again, we always mention in our write-ups that figures differ. It depends on the cultivar’s current stage of development.

Here’s a quick guide for your reference:

Ideal Grow Room Temperatures

Cloning Stage Vegetative Stage Flowering Stage Drying Stage Curing Stage
74°F to 78°F 70°F to 78°F 68°F to 75°F 65°F to 74°F 68°F to 72°F

Cloning Stage

Regardless of the type of medium you plant your clones into, they thrive best in a warm and humid environment. It would be between 74 to 78°Fahrenheit. Although, you still have to ensure that you won’t go overboard with the temp and humidity (over 90%). As this may also post risks of rotting or developing molds.

Vegetative Stage

This is the phase where the plants start to grow its leaves, branches and continue to expand its roots. Exposing it in both very cold and hot temperatures may halt the plants development. They may even run the risk of killing it. Thus, it is best to keep the temps around 70°F to 78°F.

Flowering Stage

In this period, it is ideal to maintain a bit cooler environment at 68°F to 75°F to grow the best bud quality. Lowering the temperature will likely produce the best bud color, density, and aroma. Especially, during the second half of the flowering stage. It also increases the production of trichomes as well.

Drying Stage

It is in the drying stage where the moisture gets drawn out from the plants. Hence, you need to make sure that you are pulling the wet air out. But, don’t blow the fans towards its branches to avoid drying the plants. As much as possible, try to uphold a temperature range of 65°F to 74°F.

Curing Stage

In its final stage, individual buds already feel like popcorn dry on the outside. You may now cut them away from the branches and store them in container jars. Curing is best undertaken in a cool and dark place between 2 to 8 weeks or even more depending on the strain. Sustain the temperature setting of about 68°F to 72°F.

How cold is cold?

We have already established the ideal temperature inside the grow room. But, at what particular range can be then considered as too cold grow room for the plants?

The thing with room temperature is that it never stays consistent throughout the day. It is more like a cycle, it rises during daytime and falls by night time. So during these coolest hours, be more thorough in monitoring the grow rooms temperature levels.

During the winter season, it is also quite expected already for temps to drop way below the suitable. So before its onset, you must have already planned and prepared for interventions. This is to aid in the warming of your grow space.

Moreover, there would be significant differences too in the minimum and maximum limits for the warm and cold-season crops.

Season Daytime Temperature Night Time Temperature
Warm Season Up to 75°F Not lower than 60°F
Cold Season Up to 60°F Not lower than 50°F

Any temperature beyond the said numbers can be already considered as too cold for the plants to grow in. Thus, appropriate warming measures must immediately be rendered to prevent harming the cultivars. 

To help you conveniently monitor the accurate temperature levels of your grow room, it would be very useful to install a thermometer device. 

Here are some of our top picks:

  • Analog thermometers:

General Tools A600FC High-Temperature Analog Thermo-Hygrometer

Reotemp Analog Wall Thermometer & Hygrometer

Amtast Dial Type Barometer Thermometer & Hygrometer

  • Digital thermometers:

Govee Thermometer & Hygrometer

Vivosun Digital Indoor Thermometer & Hygrometer

Oria Indoor/Outdoor Digital Thermometer w/ 3 Wireless Sensors

Plant symptoms indicating the grow room is too cold

You may have neglected to detect or maintain the appropriate temperature in your grow space. Here are a few of the symptoms you can look into. This is to check if your plants are experiencing distress from intense coldness.

  • Weak and stunted growth.
  • Some or most parts of the plant are damp.
  • Formation of molds.
  • Changes in yield and color.
  • Unpleasant smell and taste of the plant.
  • For hydroponic systems, the root becomes chilled or frozen.

If your plants are showing any of the above symptoms, start the warming measures. It will help you to restore the health of the cultivar and rescue it from imminent death.

Problems that may arise from a too cold grow room

The following are the possible issues that are likely to occur due to the unsettling coolness of the grow space.

Unhealthy Grow Environment.

Too low temperatures can leave the room with uneven distribution of heat. Hot and cold spots tend to pop up here and there. Thus, causing the environment to become damp. The mere presence of unwanted wetness can prompt the rotting of the buds. Moreover, this can also precipitate the formation of pests and molds. Hence, even bacteria and fungi.

Read Also: The Necessity of Carbon Filter for Your Grow Room

Affliction in any of the above can cause severe damage to the cultivar. Worse, it can even lead to its demise if not addressed immediately.

Diminished Germination.

In order for germination to take place, it is ideal to maintain a temperature between 65° to 75°Fahrenheit. Thus, even up 80°F for warm-season cultivars. But, if your grow space is somewhere below 60°F, it is too cold for the process to start. As a result, the plants might only end up producing low and poor-quality yield.

Increase Oxygen Concentration.

Basically, if the grow rooms temperature is way below the normal, it can induce the chilling of the liquids. This, in effect, increases the concentration of oxygen in the water.

Oxygen itself is essential for plant growth. Yet, absorbing too much oxygen from the roots has an adverse effect too. Very high O2 levels can disrupt the metabolic and enzymatic processes. So, this hinders the most growth of the cultivar.

How to deal with a too cold grow room?

We have already presented the various problems mentioned above. Here are a few of the ways you can resolve the issues with the low temperature inside your grow space.

1. Provide Good Room Insulation.

You would need to provide enough insulation. This is one of the most basic things you can do to prevent too cold temperatures in grow room. The insulator will aid in the conservation of heat from within. Rather than getting it wasted and released out of the space.

Ideally, you should plan and establish this during the set up of your grow area. Especially if your location is bound to experience a winter season. Although, insulation doesn’t pertain only to airflow ducting. There are also alternative methods you can provide the plant the insulation it needs.aluminum foil sheets

  • If planted in pots – wrap it with aluminum foil sheets.
  • If the container is in direct contact with the cold floor – place it on top of a polystyrene plastic sheet.polystyrene plastic sheet
  • Or, better yet if possible, you can also conceal the entire grow tent from the outside.

2. Promote Sufficient Air Circulation.

It is vital to promote proper air circulation during this period. An excellent way to do that is through the use of an oscillating fan. So, it would be more efficient to let the fan sweep side to side or up and down to further ease the movement of air. Rather than focusing the airflow direct towards the plant. Doing such helps with even distribution of heat across the grow space. Hence, eliminating the chances of developing windburn and micro-climates.

Our top picks for oscillating fans:

Vornado Pivot3 Compact Air Circulator Fan w/ Pivoting Axis

Secret Jardin 30W Monkey Fan For Grow Tent Poles

Vivosun 6 Inch Clip On Oscillating Fan 2 Pack

Woozoo Oscillating Table Fan

Vornado 560 Whole Room Air Circulator Fan w/ 4 Speeds

3. Adjust Lighting Periods for Too Cold Grow Room

Most indoor growers practice running the light in the morning and turning it off by night. It would help to simulate the normal day and night cycle as it is outdoors. Nonetheless, if it’s winter, a recommendation would be to reverse the schedule for the time being.

Running the lights during the night instead of the usual mornings will help to provide extra warmth. Considering that light bulbs do emit certain amounts of heat. Even some would think this is a good way to help mitigate the coolness of temperature. The light cycle cannot go on for 24 hours straight. Your plants still need some time of darkness so that they can bloom as well.

You may use temperature timers or controllers to help you regulate the schedules.

Our top picks for light timers:

  • Mechanical Timers

Fosmon Indoor 24 Hour Mechanical Outlet Timer

GE 24 Hour Heavy Duty Indoor Plug-In Mechanical Timer 2 Pack

iPower 24 Hour Programmable Plug-in Mechanical Electric Outlet Timer 2 Pack

  • Digital Timers

FosPower 7 Day Programmable Light Timer

Nicrew 7 Days Digital Programmable Plug-in Outlet Timer

Nearpow Multifunctional Infinite Cycle Programmable Plug-in Digital Timer Switch

4. Provide Heater Fans if Grow Room is Too Cold.

The heat generated by the light system contributes to the warming of the grow space. It is not enough to sustain the heat within the room. And so, the provision of extra heating devices such as heater fans is still necessary in most cases. Especially during the winter season.

There is a catch though in using heater fans. This is only applicable to grow areas with high humidity. That is because the fan tends to release dry hot air that can lower the relative humidity in the room. So, driving the RH levels too low can ruin the health of your cultivars.

Our top picks for heaters:

Garage Space Portable Electric Heater Fan

Sendow Portable Electric Space Heater

Isiler 1500W Portable Indoor Space Heater

Buyplus Portable Electric Garage Greenhouse Heater Fan

iPower Electric Greenhouse Heater Fan

5. Invest in an Oil-Filled Radiator Heater.

If budget permits, it would be a good idea to invest in an oil-filled radiator. This appliance usually comes with a thermostat controller. This will help you adjust the heat. Moreover, its design is often compact. Thus, you don’t have to worry about it occupying too much space in your grow area.

Our top picks for radiator heaters:

DeLonghi Oil Filled Radiator Space Heater 

Optimus H-6003 Portable Oil Filled Radiator Heater Mini

Costway 700W Portable Oil Filled Radiator Heater w/ Adjustable Thermostat

Pelonis 1500W Electric Oil Filled  Radiator Heater w/ Safety Protection

Heatzone 1500W Electric Oil Filled Portable Space Heater w/ Adjustable Thermostat

6. Warm the Soil with Heat Mats.

Along with the cooling of the air, the plant’s soil and root systems also suffer from low temperatures. As a consequence, it won’t be able to take in as much water and minerals. Thus, hindering the growth and development of the plants.

Besides, a warm ground is also essential in order for the process of germination to take its course. As mentioned earlier, you should maintain a temp between 65°F to 75°F to propagate the seedlings.

To aid in the heating, you can place several heat mats on top of the soil. This would regulate the temperature back to a comfortable level.

Our top picks for heat mats:

Ohuhu Seedling Heat Mat

Propagate Pro Seedling Heating Mat

Hydrofarm MT10009 Hydroponic Pad

iPower GLHTMTLX2 2 Pack Durable Waterproof Seedling Heat Mat

Vivosun 2 Pack Durable Waterproof Seedling Heat Mat

7. Warming of Water or Nutrient Solutions.

In the case of media-less or soil-less cultivars, heat up the water or nutrient solution. This is another clever way to help warm the plant and help better absorption. Its absence of insulation makes them more prone to getting chilled. Thus, all the more reason you should warm the solution.

Careful though not to heat the liquid too much. Rather, you should warm it up to room temperature only. Way too hot solutions can actually burn and damage the roots. You may use aquarium heaters as well. It would help sustain the favorable temp of the liquid with much better control.

Our top picks for aquarium heaters:

Eheim Jager Aquarium Thermostat Heater

Mylivell Aquarium Submersible Heater

Hygger Fast Heating PTC Aquarium w/ LED Digital Temp Controller

Zeetoon Aquarium Heater w/ LED Digital Thermostat Controller

Inkbird Aquarium Heater w/ Waterproof Sensor

There you have it! There will always be situations wherein we cannot avoid having extreme weather conditions. What winter brings to us is out of our hands to handle. Besides, we have proven that it is not impossible to carry out countermeasures. Thus, to maintain the conduciveness of the grow room even throughout the cold seasons.


Gary Stephen
Gary Stephen

Hi, I am Gary Stephen. I have been gardening for a long time. Gardening gives us much benefits and pleasure. Many of us desire to have a garden, but it cannot fulfill the desire for the proper guide or instruction of gardening. So, I am eager to help them. For this purpose, I have developed the website to make a garden with the proper guide. So, you will get me beside you if you want to know anything about gardening.