While surveying your lawn for cold damage you may also find areas that contain grassy weeds. Now is the time to dig out these areas or use a non-selective herbicide (example: Roundup) to kill the crabgrass. Also, rake out the area and loosen the top 3 inches of soil to allow healthy new root growth. These areas will need to be resodded after 10-14 days per the label directions on herbicide. It is important to watch these areas closely as weed seeds may be contained in the soil and may germinate after sod is put down. Pull any new emerging crabgrass by hand and give the new sod the proper water it needs and these areas should re-establish into a healthy lawn with no crabgrass.