here in tn, grass is green. temps warming into 60s lows 30-40. will still be cold spells at night for a few more weeks. does cold have a lot of affect on Fertilize? always people putting it out 2-3 weeks out before me.
Ground temps have to be warm enough for your grass to grow. If you fertilize and then have a temperature dip, your grass isn't utilizing your fertilizer.
P&K in the fall, nitrogen when the grass starts really growing.
To add to that, P& K can take 3-4 months to break down and really work good, N can start within days and be gone by 90 days or so. Most use them as them all work the same.