Precipitation anomaly (deviations from the 1901-1960 average, inches) for annual (black), winter (blue), spring (green), summer (red), and fall (orange), for the Midwest U.S. Dashed lines indicate the best fit by minimizing the chi-square error statistic. Based on a new gridded version of COOP data from the National Climatic Data Center, the CDDv2 data set (R. Vose, personal communication, July 27, 2012). Trends are only statistically significant annually and for the summer season. Note that the annual time series is on a unique scale. Trends are upward and statistically significant annually and for the summer season.