I'm BP 1 and suffer from SAD, as well. I, too, live in the northern climes & depression hits hard after the shift in daylight savings time through February. I use a light box, and my pdoc prescribes a low doe of AD in the winter months to combat SAD. Like anything else, my pdoc & I monitor things to make sure I don't go into a manic or mixed state. I'm fortunate to have a pdoc willing to see me on a more regular basis during these months. I wish I could say the light box and low-dose AD always work, but the winter is always a struggle for me despite these measures. I do, however, use both treatments & have been able to get through many winters doing so.

If you're interested, light boxes can be very inexpensive. Examples can be found here on Amazon:

Amazon.com: light boxes for sad