Growing Weed Indoors in Winter: How to Keep the Cold Out of Your Grow

How to grow weed indoors in winter

To grow weed indoors in winter, keep the cold away from your plants: get containers off cold concrete floors, pick a room with few exterior walls, lean on your grow light's heat (long autoflower light schedules help) and hold about 25-30 °C (77-86 °F) with lights on and 18-22 °C (64-72 °F) with lights off. Some growers get nervous about growing cannabis in cold climates, indoors or out. Yes, cold weather throws extra challenges at cannabis growers. But it also brings some advantages and opportunities. It can be easier to grow buds with fall colors, for example, or to keep your grow room from overheating. With good planning and the right cannabis seeds, growing in a cold climate isn't just doable, it's pretty straightforward and can even come with some surprising perks.

Growing indoors can look like the best approach when the weather's too cold and the outdoor season is too short. An indoor grow lets you dodge the worst of early- and late-season weather.

What to watch for in a winter indoor grow

Plenty of people consider it relatively easy to grow quality cannabis indoors, but cold weather adds a few things to think about. If you're growing on a cold concrete floor, you may notice heat draining fast out of the root zone. That can slow growth way down, hurt quality and mess with nutrient uptake if temps drop too low for too long. If your grow room runs too cold, your results will fall well short of expectations and the harvest can be a letdown.

When you're growing indoors in a cold climate, think about which room or space you use. If you have the option, avoid a room with lots of exterior walls. Those can drag the room's temperature down further than you'd like, especially during "lights off."

That's why a lot of indoor growers run autoflowering seeds through the winter months. With 20 hours of light a day (or even 24), your grow light can help keep the grow room warm. Worth noting, though: some of the newer, more efficient LED grow lights don't give off much excess heat. Older HPS lights, on the other hand, throw off plenty of heat, which can come in handy during winter grows.

Temperature is a huge deal in any grow. Your grow room should stay between 25 and 30 °C (77-86 °F) during the day. At night the temperature drops, and that's actually part of how the plants develop. The plant needs its rest, with lights off and a cooler temperature than during the day, ideally between 18 and 22 °C (64-72 °F). 

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