AbstractTwo years of rainfall acidity data for the eastern United States were analyzed. The data consist of rainfall‐event pH measurements from a nine station monitoring network. A spatio‐temporal stochastic model, including deterministic components for seasonal variation and rainfall washout, and stochastic components for spatial, temporal, and measurement variation, was fitted to the data. The fitted autocorrelation structure from this model was used, in the process known as Kriging, to obtain BLUE contour maps of seasonal and rainfall adjusted yearly average pH over the monitoring reg