My therapist pointed out to me that I always seemed to call her around the Spring Solstice. Coincidence?
Living in Utah the lack of bright sunlight through the late fall and winter months has an impact on my mood. I think I've got everything handled and around March I'm down and reaching out to my therapist.
Keep your face to the sun and you will never see the shadows-Helen Keller
Getting bright sunlight soon after you wake up can help with mood and with sleeping. Dr Nedley encourages the exposure to bright light to happen within 30 minutes of waking up. If that can't happen because of lack of sunlight due to weather or season a light therapy appliance can assist.
Therapeutic light boxes need to be 10,000 LUX to be effective. Dr Nedley also reports that therapeutic blue light (460 nm) can also be effective.
Here's something to try: when you can get your sunlight naturally, when weather/season prevents that use your light box in the morning as you have breakfast, read the newspaper or other morning routine. If you have a hard time staying asleep you may need to use the light box in the afternoon as well as the morning.