A 15 year climatology of the spatial and temporal patterns of stable isotope ratios (HDO:H₂O and H₂¹⁸O:H2O) of rains and water vapor in hurricanes and tropical storms over land in the United States is presented and related to the water vapor source, the spatial and temporal distributions of precipitation, and the degree of extratropical transition using MM5 simulations. Most hurricane rain and water vapor samples possess distinctly lower isotope ratios than typical of either the tropics or summer conditions, but extremely low isotope ratios only occur near storm center either after the region of high winds has moved inland or when samples are collected far downwind from the ocean. The isotope ratios thus corroborate the finding that the inner region of high winds over the ocean is a significant water vapor source for hurricanes.