Maybe I mistaken but I thought the summer light was on the white/blue spectrum and the winter light on the yellow/red spectrum....that's why we use differents light to grow our favourite flower, mercure light to grow up and sodium light for blooming...isn't it?In the winter we have a blue sunlight if you look at vapor with 6400k temp light it will look awesome. A 2400k temp light (closer to the red spectrum like candle light) you won't see it very well such as in summer. Why the winter has blue light and summer has red light is the way the angle the suns rays hit the atmosphere I think.