Outdoor Marijuana Temperature Range: Ideal, Okay, Extreme
Not sure if your climate supports outdoor cannabis growing? Find out how low temperature and cold weather affect your harvest
If your climate is too cold (like mine), or too hot, and you think that the only option for you is indoor cultivation, think again. The acceptable outdoor marijuana temperature range is quite wide, and marijuana plants, at least mature ones, can be surprisingly hardy. As a result, they can take a lot of bad weather and still reward you with enough high-quality buds.
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Ideal Outdoor Marijuana Temperature
Well, ideal outdoor marijuana temperature is actually the same for any type of grow. It’s because indoors we simply try to recreate artificially the natural environment that cannabis plants have best adapted to. The only difference is that, in an indoor setup, we have more control in maintaining the perfect conditions. And they are:
77-86°F (25-30°C) during the day, or when the lights are on.
At least these are the figures that are the most conducive to photosynthesis and gas/water exchange processes, according to research 1 . And, in case you’re wondering, the ideal level of light intensity (PPFD) would be
All this may guarantee the fastest rate of growth for cannabis plants. However, our goal is a bit different — we grow for the highest possible production of THC and other cannabinoids, as well as terpenes that make the smoke so aromatic and flavorful. So, with that in mind, growers have gradually come up with the following empirical figures:
- Seedling and vegetative stage. Young weed plants prefer a little milder conditions than the flowering ones, with day temperature between 70 and 85°F (20-30°C).
- Flowering stage. When plants start to form buds and then all the way to harvest, the temps should be a little lower — 65 to 80°F (18-26°C). The reason is that higher temperatures burn terpenes and cannabinoids making the buds less aromatic and potent.
During any stage of growth, the night temperatures should be 10°F (8°C) lower than during the day. This gives marijuana plants a chance to shift to a lower gear and have a rest. However, too radical a change between day and night temperatures can lead to even more stress, and should be avoided.
That Was Ideal, But What is Acceptable?
Outdoors, we work with what we have. Even in climates that give us the luxury of the perfect outdoor marijuana temperature range there are spells of too cold and too hot weather. So the question is: what is okay for outdoor weed and what is not?
Just like a dashing bachelor in a Jane Austin novel who chooses himself a wife, anything from 15 to 30 would do just fine. (Sorry for this potentially offensive remark, but in my experience they are the most memorable.) These figures are in Celsius btw, and in Fahrenheit it’s 59° to 86°.
At higher temps, no irreparable damage is done, although the photosynthesis slows down. And so does the THC production, while terpenes evaporate from buds at a faster rate, robbing them of flavor. The texture of buds deteriorates as well, and they become less compact and more airy.
So if you live in a really hot climate, like Arizona or Nevada, try to mitigate the effects of heat stress. Make sure that trees, walls or other structures provide some shade for your marijuana during the hottest hours in the afternoon. Or stretch some shade cloth over your garden (60% transparency should be just fine). Anyway, if higher temps may hurt weed plants, they can’t kill them. Drought can though.
The effects of cold temps are much worse. When the daytime temperatures drop below 15°C (59°F), all processes slow down to a crawl or are put on pause. And at 13°C (55°F), more delicate strains may experience a shock. It means that once the temps are back within the acceptable range, the plants will need some time to recover before they resume bud production.
The Effects of Frost and Snow
Below freezing air temperatures don’t kill marijuana overnight, but they can do a lot of damage to leaves, flowers, and even branches. They wilt and get brown and mushy in places, so if there’s a chance of snow or even a couple of frosty nights in a row, it’s best to harvest your buds before that.
These buds might be still salvageable, but the quality will be very subpar, to say the least.
I myself once harvested a couple of bushes after a heavy snowfall. They started to flower extremely late, so I had to push the limits with them. When I was cutting the branches, I had to shake them very hard to free them from snow. Only a minor percentage of buds were spoilt beyond being usable, but the rest turned out okay. I don’t recommend this to anyone, though. It’s safer to use a faster-flowering variety or an auto.
How to Protect Cannabis from Cold
1. Choose Genetics Wisely
Start with choosing a strain that is fast enough to finish flowering before the end of the growing season. The only sure thing are autoflowers because in practically any climate there are a couple of warm months in the middle of summer, and it’s all an auto needs. Besides being very quick to finish, autoflowers are more resilient to cold weather: they have Cannabis ruderalis genetics in them, and ruderalis is a subspecies that originated in places like Siberia and is very tolerant of cold.
This is a natural ruderalis plant. Looks pathetic, doesn’t it? Luckily, modern autoflowers are so much better in every respect.
If you prefer to grow a photoperiod variety, look for strains with words ‘fast’, ‘early’ or ‘quick’ in their names. They are the result of crossing a true photoperiod strain with an autoflowering one. These plants still wait for the days to become short enough before they start flowering, but this happens much earlier.
Important! When shopping for an outdoor photoperiod strain, take with a grain of salt the harvest times that a breeder promises. If, for example, they say late September, they probably mean places like Spain or Southern France, not Scotland or Denmark. The farther up north, the longer the summer days, and the later the flowering begins (and finishes). That’s a ‘perk’ of living at higher latitudes.
2. Find a Good Spot
The second most important thing is finding a spot that receives as much sunlight as possible and is sheltered from wind. It also helps to plant your cannabis near a wall (preferably a stone wall) that shelters it on the north side and is warmed by the sun. And by all means avoid planting your cannabis in a low spot. The thing is that cold air tends to ‘roll down’ from higher places into depressions in the ground, and then stays there. A south-facing slope makes for an ideal spot for your outdoor garden.
3. Using Pots Increases Mobility
Another trick that’ll help you make the best of your cold climate is growing your outdoor marijuana in pots rather than in the ground. In this case, you can move the pots around, always choosing the sunniest and warmest spot and even take the plants inside if their very survival is under threat.
4. Start Seedlings Indoors
Keep in mind that, while mature plants don’t mind some cold weather, young seedlings do. They may be shocked or killed if the temps are outside the acceptable range. So make sure that summer weather has come for good—no ground frosts in the early morning and at least 15°C (59°F) during the day—before taking the seedlings outside. Also, it’s recommended not to sow cannabis seeds directly into the ground. It’s best to grow them for 2 weeks inside, then harden them a bit by taking outside for a couple of hours every day, and finally place them permanently outdoors.
Outdoor Marijuana Temperature: Focus on the Root Zone
One thing that is overlooked by most growers is that the temperature of the air plays a far less important role than that of the medium. The air may be as cold as 5°C (41°F), but marijuana plants will thrive if the temp in the root zone is at a comfortable level 2 . It’s like when you are neck-deep in a hot spring, you don’t mind that your head is exposed to a chilling breeze, right?
Remember all those numbers we’ve given above? They all apply to the root zone.
This really gives you a lot of freedom. The most obvious choice is to use a really thick layer of mulch to insulate the ground from the air. It works both ways, by the way: by keeping the ground cooler in hot climates, or keeping it warmer in cold ones.
Or you can go high-tech. A pump, a water tank with a heater/cooler and some clever piping laid in the ground or through the containers/grow bags will allow you to circulate water with a set temperature to warm up or cool down the medium. (And mind you we’re not talking about watering here, right? Watering is a different story. This is only about heat exchange.)
Also google ‘geothermal greenhouse’. This is basically an underground (or partially underground) greenhouse with a glass roof that is generally made sloping and facing south. A geothermal greenhouse makes use of the fact that deep below the ground surface the temperature remains stable throughout the year. It’s much cooler in summer, and much warmer in winter compared to above ground. For such a greenhouse to really work its magic the depth must be 10-12’ (
Outdoor Winter Grow
Wanna try and grow marijuana in winter? First check if your climate supports this idea. Again, the temperature, especially in the root zone, should be above 15°C (59°F) most of the time. Short periods of colder weather are unwelcome, but acceptable. Opt for cold-resistant strains, like Indica autoflowers. Also, use all the tips and tricks of protecting your plants from cold that we’ve shared above. And again don’t forget about the importance of the root zone).
Also keep in mind one more thing about marijuana winter grows: the days in winter are short, and the nights long. This will make any photoperiod variety start flowering after just a few weeks from sprouts. It’s not unlike the ‘12/12 from seed’ method. This usually results in much smaller plants, so if you want them bigger, think about auxiliary lighting to make the days longer.
If you don’t use auxilliary lights to extend short winter days, any photoperiod strain will go into the flowering mode.
Conversely, if your winter cannabis doesn’t finish before spring, or more specifically before the spring equinox (March 20), days will gradually become long enough to disrupt the flowering. So make sure you plan your winter grow accordingly.
Outdoor Marijuana Temperature Range is Quite Inclusive
Outdoor horticulture of medical marijuana is feasible even in colder climates. Just learn to make the best of the most adverse conditions and choose a strain that is quick to finish and is tolerant of low temperature. And now, after the arrival of autoflowers, almost anybody can grow top-shelf buds outdoors.
The Outdoor Grower’s Almanac
As a cannabis grower, the fun begins at the onset of the outdoor growing season.
However, when does the cannabis growing season start? Furthermore, when does the outdoor marijuana growing season end? Dig into our Outdoor Grower’s Almanac to find the answers you’re looking for.
You’ll discover everything you need to know about the outdoor weed growing season, such as when to plant weed outdoors and when to harvest buds. With the help of this marijuana growing calendar, you can plan your outdoor grow accordingly.
Whether you’re a beginner or a green thumb, use this guide to maximize your outdoor marijuana yield and make this growing season worth it.
The Outdoor Cannabis Growing Season According to Feminized and Autoflowering Seeds
The outdoor growing season will differ depending on your choice of feminized or autoflowering seeds.
Here’s a list of feminized characteristics that you must be aware of:
- Require the length of the growing season to complete a full cycle
- Produce hefty yields
Next, here’s a list of autoflowering characteristics that you must know:
- Non-photoperiodic (do not require a specific amount of light hours to flower)
- Contain an internal clock to begin the flowering process
- Allows growers to complete multiple harvests within a single growing season
- Grows and flowers quickly
- Produces less bud compared to feminized seeds
As you can see, both types of cannabis seeds have advantages and disadvantages. However, the growing calendar is different depending on which you choose.
Let’s take a brief look at the growing season for both feminized seeds and autoflowering seeds.
The Outdoor Growing Season of Feminized Seeds
In its entirety, the growing season of feminized seeds lasts between April to November in the Northern Hemisphere and September to May in the Southern Hemisphere.
Depending on your region, you may experience a longer or shorter growing season as the weather shifts from spring, summer, and, eventually, fall.
As a special note, we’ve added the growing season months for the Southern Hemisphere. If you’re growing marijuana in Oceania, Southern Africa, or South America, the growing season starts and ends at drastically different times than regions in the Northern Hemisphere.
Let’s take a look at how the growing calendar starts and ends for feminized marijuana seeds.
Phase One — April (September in The Southern Hemisphere)
The outdoor growing season for feminized seeds typically starts in early April (September for the Southern Hemisphere).
Although your region may experience frost this early in the season, you can germinate the feminized seeds indoors. By doing so, you will have a jump start on the outdoor growing season.
If you haven’t yet, read our guide on how to germinate cannabis seeds.
You can germinate weed seeds by using paper towels, rooting cubes, or soil.
Phase Two — May (October in The Southern Hemisphere)
Once the threat of frost has passed at the beginning of May (or October in the Southern Hemisphere), it’s time to plant your feminized strains by transplanting the cannabis seedlings in the ground or containers.
By this point, spring is in full swing, and each day brings longer daylight hours. As daylight increases, so does the growth among your marijuana crop.
By this point, you should:
- Check marijuana seedlings and juveniles daily
- Provide additional nutrient content
- Prevent over-watering by closely monitoring water uptake
- Protect from the elements (rain or wind)
Phase Three — June (November in The Southern Hemisphere)
By June (or November in the Southern Hemisphere), the days are long, and your feminized strains will produce explosive vegetative growth.
At this point, you should prepare support structures and trellis netting in anticipation of the flowering stage.
Additionally, this is the perfect stage to incorporate cultivation techniques to increase yield, such as:
- Super cropping
Although each of the techniques mentioned above are stressors for the cannabis plant, they will bounce back quickly and resume normal growth.
Furthermore, you should:
- Feed your marijuana plants additional nutrient content via amendments or concentrated bottled nutrients (vegetative-specific)
- Prune lower growth to increase airflow
- Monitor for insect or disease outbreaks regularly
Phase Four — July (December in The Southern Hemisphere)
July (December in the Southern Hemisphere) is the final month of vegetation.
At this point, you’ll be shocked by the massive growth of your cannabis plants. By this point, you will notice your cannabis plants require a lot of water, nutrients, and sunlight to fuel their epic growth.
As long as you’ve followed our guide on How to Grow Marijuana Outdoors, your outdoor weed garden should explode with greenery.
Phase Five — August (January in The Southern Hemisphere)
Once August ( January in the Southern Hemisphere) appears, you’ll notice a change in your cannabis plants.
The nodes suddenly, as if out-of-the-blue, produce bud sites. The sudden burst of white pistils marks the beginning of the flowering stage, or better yet, the pre-flowering stage.
At this point, your marijuana crop will undergo what’s known as pre-flower stretch. In some cases, cannabis plants may stretch 2-3x their current size over the next two weeks.
Furthermore, the per-flowering stage is an excellent time to:
- Lollipop the underside of marijuana plants
- Ensure supports are ready to take on increased flower weight
- Inspect for disease or pest outbreaks
- Change the feeding schedule to a flower-friendly mixture
- Incorporate bloom boosters into the feeding schedule
When you begin to see pre-flowers, your plants are entering the flowering stage.
Phase Six — September (February in The Southern Hemisphere)
Once September (or February in the Southern Hemisphere) begins, you’ll experience a steady stream of excitement as each day brings more weight to the flowers.
If you’re located in a region where cold weather prevails at the onset of fall — it’s best to choose fast flowering weed strains that finish by the 7-week mark. Any longer and you may lose your beloved crop to rain, frost, or snow.
Depending on the strain, harvest time may be extremely near. Remember, your cannabis seeds will have an estimated flowering window. Therefore, a 7-week strain will finish by the end of September.
Once you verify with a loupe that the trichomes are ready, it’s time to pull out the clippers and harvest!
If your cannabis plants are not ready to harvest by September, you must:
- Keep a close eye on the buds for bud rot
- Add natural bloom boosters to the feeding regimen, such as bat guano
- Ensure the support poles are propping up the buds
Left: Make sure to support the weight of your buds with bamboo sticks or a trellis. Right: Check closely for bud rot or pests.
Phase Seven — October (March in The Southern Hemisphere)
If your strain finishes flowering in 8-10-weeks, October (or March in the Southern Hemisphere) is your harvest month.
By this point, the flowers will be large and drenched with resin. Once you verify that the trichomes are ripe with a magnifying glass — it’s time to cut the plants down and begin the harvesting process.
Most outdoor cannabis growers that live in cold regions have already harvested by this point. However, if you live in a Mediterranean climate, the outdoor growing season usually ends by late October.
During October (or “Croptober”) is when most outdoor plants will finish.
Phase Eight — November (April in The Southern Hemisphere)
November is the deadline for the outdoor marijuana growing season. If your plants aren’t done — you need to make immediate plans to begin harvesting.
Nearly every region experiences frigid temperatures in November, which makes it impossible to grow weed. However, Mediterranean climates march on and allow cannabis cultivators to push their crops to the limit.
However, you must be on guard until harvest day to prevent damage from wind, rain, frost, and the increased likelihood of mold.
The Outdoor Growing Season of Autoflowering Seeds
One of the most popular methods to grow cannabis outdoors is with the help of autoflowering seeds.
Unlike feminized seeds, autoflowering strains do not rely on day length. Instead, auto strains utilize an internal clock that forces the plant to flower quickly. Therefore, you can produce multiple harvests in your garden in a single growing season.
Let’s take a look at how you can produce multiple harvests with autoflowering seeds.
Autoflowers grow and flower quickly, allowing you to have multiple harvests throughout the year.
First Autoflowering Season From May – June (October – November in The Southern Hemisphere)
- Germinate a fast-flowering auto strain, such as Auto GDP, at the beginning of May
- Care for the plant by following our guide on How to Grow Marijuana Plants Outdoors
- Harvest by the end of June
Second Autoflowering Season From July – August (December – January in The Southern Hemisphere)
- Germinate a fast-flowering auto strain, such as Auto Widow, at the beginning of July
- Care for the plant by following our guide on How to Grow Marijuana Plants Outdoors
- Harvest by the end of August
Third Autoflowering Season From September – October (February – March in The Southern Hemisphere)
- Germinate a fast-flowering auto strain, such as Auto Bruce Banner, at the beginning of September
- Care for the plant by following our guide on How to Grow Marijuana Plants Outdoors
- Harvest by the end of October
Which Cannabis Seed Fits Your Growing Season?
Now that you understand how long the cannabis growing season is — which seed type fits your schedule?
As you can see, feminized marijuana seeds are perfect for those that want to experience massive yields, gigantic plants, and sky-high cannabinoid levels.
On the other hand, autoflowering genetics empower you with multiple harvests and a hands-free approach.
Regardless of your choice, you’ll be satisfied every morning as you look over your outdoor marijuana garden. Once you have your first outdoor growing season under your belt, it’s time to look ahead — and start planning next year’s outdoor cannabis cycle!