First of all, does this weed and feed contain a preemergence herbicide to control crabgrass, or is it a post emergence herbicide to control broadleaf weeds such as dandelions? I checked the Enviroweather website for the weather station located on the MSU campus, and soil temperatures have been above 50 degrees F for a few days now, so soil temperatures are warm enough for crabgrass seed to start germinating. If the weed and feed contains a pre-emergence herbicide that is meant to control crabgrass, you can apply it now. Apply it according to the label directions to get the correct amounts. There are usually recommended fertilizer spreader settings listed on the bag. If your weed and feed is meant for broadleaf weeds, you can still apply it now, because the broadleaf weeds are actively growing.