I hear that fall is the best time to plant, but fall for some locations is
like winter for others. My lawn is a mess and I need to replant. Is early
October too late to plant new grass seed in New Jersey?

I live in Northern New Jersey near New York City area. I planted grass
seeds in early September. The fine fescue has germinated after just
one week. The Kentucky blue grass hasn't germinated yet, and I am
hoping that they will start germinating in one week -- or else...

In other words, I have planned for having grass seeds to germinate to
as late as early October (because Kentucky blue grass germinates from
2 weeks to a month). I am not saying that my plan is right; I am
saying that this is my plan and I am sticking to it for now. Let's
assume that the last possible germination period is from early October
to mid-October, you will have to act fast and use the correct grass
seeds. If my assumption is correct, you will have to use fine fescue
or something similar that can germinate in one week. And you probably
should not use Kentucky blue grass because they may germinate in early
November if you plant the seeds now, and that sounds like too late to
me.

If I were you, I will plant the grass seeds next spring just to give
myself a better chance of success. Afterall, putting top soil/compost
over grass seeds is a major effort (and I am under the impression that
doing this is the best method). I surely want this to be a success
instead of a failure.

If spring is the time that you will plant grass seeds, you may need to
use crab-grass prevention chemical that will not hurt grass seeds
germination (haven't tried that myself, I am not sure how good that
chemical will work).

Good luck whichever way you decide to do.

Jay Chan