Crabgrass pre-emergent timing model for US
 

It's about that time of year to put down crabgrass control if you need
to do it. I've seen this discussed here once in a while, but not in a
long time. Here's a timing model that uses temperatures in your area
to forecast the optimal time to apply it:

http://www.gddtracker.net/?model=7&offset=0&zip=07760


Select "crabgrass PRE" on the right side and it will show a map for
your area with early, optimum and late timing. The model was developed
for the Michigan area, but should work OK for the northern half of
the country. It's showing NJ is just entering the optimum period
and will be there for maybe the next ten days or so. Another general
guide is to put it down when Forsythias bloom, that hasn't started
here yet.

I use Dimension, which will also kill very early crabgrass plants,
so I time mine near the end of the optimal range, keeping rain
in mind as it needs a rain to water it into the soil and make it
effective. If you have crabgrass troubles most years, a second
application about 6 weeks later is a good idea too.