I have read you cannot seed your lawn for 12 weeks after applying Crabgrass Killer. We have some areas that need to be seeded in our lawn here in S/E Ontario. Do we have enough time to seed before the Crabgrass Killer has to be put on????
Seed with cheapest grass seed now. When that is 2" high, apply the pre-emergence crab grass killer. In late Aug or Sept reseed with good seed. Best I can do for you from down here. I"m not a grass specialist. Perhaps some one who is will get on and tell me what I am full of.
I disagree with using cheap grass seed anytime. What you get with inexpensive seed is a lawn that will die the first time the sun hits it in summer.
Hold off the weed killer--do that when the weeds are growing their best and seed now to get the best of the spring rains.
The soil temperature though is the key factor...we have to get some decent warm weather to affect the soil temperature so that seed will germinate properly.
By the time the grass is well germinated and high enough, it will be too late for pre-emergants. I'd skip that this year.