The paper is an overview of the work on atmospheric water budget evaluations over the North American Monsoon domain at the NOAA Climate Prediction Center. Information on the observational and model-based datasets, their availability and features, and also on the technique involved will be discussed. Upper air radiosonde observations over the Mexico and US are used to evaluate the water budget terms over the North American Monsoon region. The results which are based on about thirty year time series of atmospheric water budget components include analyses and initialize discussions about time series, mean annual cycles, mean annual variability, anomalies, long-term variations, accuracy and possible biases of estimates, and impact of zonal and meridional components of the atmospheric vapor flux.