Seattle has one of the lowest amounts of sun per year of all metros in the USA. It selects for those who are serious about work, more than weather.
My previous manager at Amazon told me he recommended everyone who came from California to take a vacation back during the winter lest they get too depressed.
Uhhh, Seattle, Portland, and the rest of the PNW have some of the most outdoorsy people in the country. We're less than 2 hours from the ocean or the mountains.
I know myself well enough to know that I am less productive when I don't get sunlight. I suspect many other people are the same.
There are successful companies that eat their workers alive, employee happiness isn't related with their success in a lot of cases.
I guarantee you anyone with a roof and a rain barrel is not hurting for water for their plants.