Climate fluctuations in Illinois, 1901-1980

Changes in climate directly affect four areas of major activity and concern in Illinois – water, energy, agriculture, and transportation. This report presents selected Illinois records for 1901-1980 on a variety of atmospheric conditions that allow assessment of climate fluctuations, climate trends, variability around the trends, and impacts of these changes on the four areas of concern. Documented are changes in statewide and regional precipitation and temperature, plus selected point (station) data. Also presented are changes in other atmospheric conditions including relative humidity, sky cover and sunshine, visibility and related air quality, severe local storms, and wind speed and direction. The historical records are carefully evaluated as to quality. Analyses of the data indicate changes in the more recent 20 years (1961-1980 vs 1901-19601 to wetter and cooler conditions: more rain and snow and fewer droughts; decreases in temperatures especially in summer and winter, with fewer extremely warm days and many more extremely cold days; increases in cloudiness and decreases in sunshine and clear days especially in summer; and increases in wind speeds with more diverse wind directions. All trends are more marked in the extreme seasons of summer and winter than in the transition seasons of spring and fall. Mixed regional changes are noted in other atmospheric conditions, and no trend is seen for relative humidity. Reference: Changnon, Stanley A., Jr. Climate Fluctuations in Illinois: 1901-1980. Illinois State Water Survey, Champaign, Bulletin 68. Indexing Terms: air quality, climate change, Illinois, precipitation, relative humidity, severe local storms, sky cover, sunshine, temperature, visibility, wind speed and direction. STATE OF ILLINOIS HON. JAMES R. THOMPSON, Governor DEPARTMENT OF ENERGY AND NATURAL RESOURCES MICHAEL B. WITTE, B.A., Director BOARD OF NATURAL RESOURCES AND CONSERVATION Michael B. Witte, B.A., Chairman Walter E. Hanson, M.S., Engineering Laurence L. Sloss, Ph.D., Geology H. S. Gutowsky, Ph.D., Chemistry Lorin I. Nevling, Ph.D., Forestry Robert L. Metcalf, Ph.D., Biology Daniel C. Drucker, Ph.D. University of Illinois John C. Guyon, Ph.D. Southern Illinois University STATE WATER SURVEY DIVISION STANLEY A. CHANGNON, JR., M.S., Chief