If you are in an area with hardiness issues, then long before now. And cut back on water if possible as well. In zone 10 it probably won't matter. But in general you only fertilize before you want growth. Not before you want the plant to slow down to increase it's hardiness for winter.
In zone 5-6 and probably 7 I'd stop nitrogen in June. Maybe sooner and in some cases none the entire yr, like in-ground on rich soil.
Let the plant tell you. If not as much growth as you want, fertilize. If too much don't fertilize again until growth is too little. And remember there is a month or two lag time.