Double cropping is increasing in dairy farming in parts of the Northeastern United States. The effect of double cropping on forage yields in this region is uncertain and there is particular concern with respect to the field water balance. In this study, we examined silage yields of double cropped (corn/rye, corn/barley) and single cropped (corn, corn/soybean) rotations. We also measured the components of the water balance: precipitation, runoff, drainage and soil water content. Evapotranspiration was estimated using the Penman-Monteith method. Field data were collected in Landisville, Lancaster County in Pennsylvania between 2003 and 2006. Double cropping (small grains) did not affect main crop yield (corn and soybean) in summer 2004 and 2005. Total annual biomass increased due to the additional small grain silage yields. Runoff was not significantly different between rotations, probably due to low rainfall intensities and durations, and low antecedent soil moisture conditions. There were no statistically significant differences in deep drainage between double and single cropped rotations. Results of this two-year trial suggest that double cropping does not negatively influence summer crop yields, and therefore leads to increased annual forage yields. Runoff and deep percolation were not affected by double cropping in these two years.  Double cropping is suggested as a viable option for dairy producers in the Northeastern US as long as temperatures permit two silage crops per year.