I went to Seattle in February during Presidents' Day Weekend in 2015, and you could wear a T-shirt, and there were hundreds of people sunbathing in parks by the water, parks that still had bright-green grass.
And SF is actually pretty consistent with temperature year-round, in the 50's-70's, my sister lived there for 3 years.
I dont think people should use 2015 as an example for how the weather usually is in the north west. 2015 was unusually hot and dry all year culminating in the warmest summer ever (portland had 30+ 90 degree days instead of the average of 13). It was so warm that in February on our mountains they were opening the summer parks.