According to the Step 1 Crabgrass Preventer plus Lawn Food product label, for best results the lawn should receive 1/4 to 1/2 inch of water or rainfall within 2-3 days of the application. We would recommend reapplying Step 1 in 4 weeks when you are not expecting much if any rainfall to control the amount of water applied.
Much like other granule pre-emergent herbicides, the Scotts STEP 1 Crabgrass Preventer Plus Lawn Food label states to apply when the grass/lawn is dry as you need the granules to reach the soil and not stick to the wet leaf surfaces of the existing plants. If you can water the product into the soil to ensure the granules move from the damp grass into the soil to benefit you the way you desire for weed prevention, this may help decrease the amount of product lost to the surface grass.
