Take one of the cones you feel is ripe. Mesh the cone b/w your finger and thumb. You may notice some moisture. If the edges of the cone are yellow and drying, it might be time for that cone. Know the moisture content of that cone(as described above).
For the younger hops, they should yield a higher moisture value when meshed.
As soon as you feel the moisture value dropping, pick 'em!
Since you are not in the higher latitudes, I don't know when is best for you. For myself(approx. 48*lat.) it is in August/Sept.
Tap-100% Chinook IIPA, Dry Stout on Nitro
6th Year- Cascade, Chelan, Chinook, Willamette
4nd Year- Hallertauer Tradition
3rd Year- Galena, Hallertauer Tradition