The answer to that depends on how much work you have to do. If you have 500 lawns to do by yourself and are just now asking that question you are already screwed. If you have a few jobs to do then no worries. Soil temps need to reach the mid 50's for several days before crabrass will germinate. In your area that give you atleast 4-6 weeks. Broadleaf ester based weed controls will work with air temps in the 50's. As far as fert and lime, do a soil test or go to a local supplier for additional recommendations.