A detailed, long term portrait of the seasonality of precipitation over the United States is developed using a 90 year climate division record. Decadal maps of seasonality are also presented, and their variability over time considered. Model output from four GCMs are analyzed with respect to precipitation seasonality over the same area, both for present conditions, and for a doubled CO2 climate. Comparison of model output to present patterns suggests that in most cases the models are doing reasonably well in matching regional details of seasonality. For the future climate, there is some agreement among models suggesting a trend toward a spring, rather than summer precipitation maximum in the mid-continental areas of the U.S.