What is the Northern Lights strain yield? Northern Lights yields 18oz/ m2 indoors and 22oz/ plant outdoors. How much THC does Northern Lights strain have? Around 18% THC. What are the origins of the Northern Lights strain? Northern Lights was first bred in the outskirts of Seattle, Washington, by crossing an Afghani Indica with a Thai Sativa. Remember, you need to expose your NL plants to at least 18 hours of light a day during the vegetative stage. Typically, the minimal light exposure is approximately 140 Watts per square foot (for incandescent light bulbs) or 35 Watts using fluorescent LED lights. Ideally, your target is 180 Watts and 45 Watts respectively.