A Search for Average, Extremes, and Runs of Unusual Weather in Iowa

Temperature and precipitation during the past decade have exhibited wide variation throughout Iowa. Is this unusual? An attempt was made to answer this question by computing various statistical parameters that characterize variation in Iowa\u27s long term climatic record. Absolute deviations were used to identify the most and least variable months and years since 1900. Overall, 1936 with a very cold winter and very warm summer was the least normal year. Runs of daily weather showed that heat and cold stress could often persist for more than 1 month. Runs of dry days were much longer than runs of wet days. Rank analysis showed that 1993 was indeed unusual relative to excess rainfall and that 1992 summer temperatures were also unusual, even though both events had comparable analogs in the historic weather record. Annual and seasonal 10-year moving means and standard deviations revealed different patterns of interannual variation between seasons. Winter was most variable, while summer, spring, and fall variability increased during the past two decades. Only during the 1940\u27s and 1960\u27s were the seasons similar for this statistical measure