My company-sponsored doctor gave me a bottle full of two _GRAM_ pills of Vitamin D, and she said she has had to give it to most of her patients.
In the dead thick of the winter, it gets dark at 3 PM (after a 10 AM sunrise), and the rain literally never stops. When it's not raining, it's misting, and it will go weeks on end with everlasting gray skies and no sunshine.
Pittsburgh, comparatively speaking, was better because it snows off-and-on instead of constantly rains, and in January, the sun starts to come out again with blue skies, whereas Seattle stays dark, gray, and gloomy until summer.
Pittsburgh also wasn't as high up of a latitude either so the sunset would never happen earlier than 4 PM, instead of 3 PM.