This page contains the links to the rainfall frequency studies done for Illinois and later the Midwest. These publications contain the expected rainfall amounts for selected storm durations and return periods (for example, the 24-hour, 100-year storm for a site in Illinois). Currently many state and local agencies in Illinois require the use of Bulletin 70 for design work. Bulletin 71 (1992) was the follow on study for the Midwest.
We have completed an initial comparison between ISWS Bulletin 70 and NOAA Atlas 14 in Illinois for the 24-hour, 1 percent (100-year) storm. For most of Illinois, Bulletin 70 still yields higher rainfall totals than Atlas 14. The complete analysis can be found here.
Huff, F. A., and J. R. Angel, 1989. Rainfall Distributions and Hydroclimatic Characteristics of Heavy Rainstorms in Illinois (Bulletin 70), Illinois State Water Survey.
Huff, F. A., 1990. Time Distribution of Heavy Rainstorms in Illinois (Circular 173). Illinois State Water Survey. This is a valuable companion guide to Bulletin 70 and 71.
Huff, F. A. and J. R. Angel, 1989. Frequency Distributions of Heavy Rainstorms in Illinois (Circular 172). Illinois State Water Survey. This is a condensed version of Bulletin 70.
Huff, F. A. and J. R. Angel, 1992. Rainfall Frequency Atlas of the Midwest (Bulletin 71). Illinois State Water Survey.
