Spring and Fall, NW to N Spring means March to June, Fall is September to end of October, though it can work through the winter as well.
Summer usually finds it fogged out.
This site was pioneered by hang gliders over 20 years ago. Paragliders found it in the early 1990's. I have flown it 5 years, and know what he means. Anything over 10 degrees E and you are doomed. True West is very rare and transitory.