This page contains the links to the rainfall frequency studies done for Illinois as well as the Midwest. These publications contain the expected rainfall amounts for selected storm duration 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 (1989) for design work. Bulletin 71 (1992) was the follow-on study for the Midwest.
March 2019: Update to Bulletin 70
J. R. Angel, and M. Markus, 2019. Frequency Distributions of Heavy Precipitation in Illinois: Updated Bulletin 70, Illinois State Water Survey. http://hdl.handle.net/2142/103172
Huff, F. A., and J. R. Angel, 1989. Rainfall Distributions and Hydroclimatic Characteristics of Heavy Rainstorms in Illinois (Bulletin 70), Illinois State Water Survey. http://hdl.handle.net/2142/94574
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. http://hdl.handle.net/2142/94492
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. http://hdl.handle.net/2142/94490
Huff, F. A. and J. R. Angel, 1992. Rainfall Frequency Atlas of the Midwest (Bulletin 71). Illinois State Water Survey. http://hdl.handle.net/2142/94532