True crabgrass is an annual, it will die this winter. It sprouts in the spring. Use a pre emergent on it BEFORE it sprouts. You cannot see it sprout, if you can see the crabgrass growing it’s too late for a pre emergent. When the forsythias bloom is a great time.

Don’t apply lawn products when snow is on the ground. It’s A foolish waste. Follow the directions, they know how their products work.