There are three factors that you need to consider when growing marijuana seeds during the winter months: Light Temperature Humidity In order to grow marijuana during the winter, you need to make sure that they receive sufficient light, warmth, and humidity. Light Requirements: The amount of light that your plants receive plays a huge role in determining how fast they will grow. In order to get the maximum yield, provide them with at least 12 hours of light every day. If possible, try to give them 16 hours of light per day. This can be achieved by moving your plants closer to a window or by using artificial lights such as LED lights or fluorescent bulbs. Temperature Requirements: The temperature in your grow room should be between 70-85 degrees Fahrenheit during the day and 60-70 degrees Fahrenheit at night time. Make sure that you set up an exhaust fan or ventilation system in order to maintain this temperature range throughout the day and night. You can also use fans or heaters if needed in order for your plants to stay within these temperature ranges. Humidity Requirements: Humidity plays an important role in keeping your plant healthy and preventing diseases from spreading through them. You should try to maintain a humidity level between 50%-70%.