Is there a product that can be applied now to prevent weeds next year?
Typical weed and feed products will prevent current perennial weeds from coming back next year. However, a pre-emergent must be applied in spring. Many annual lawn weeds toss their seeds into the air in spring. Using a pre-emergent will prevent those seeds, and other seeds in your soil from germinating. It will be washed out and worthless by spring if you cast it now.