*Wisconsin** **State** Climatology Office*

**RAINFALL FREQUENCY GRAPHICS**

Graphs of the rainfall frequency for each of the nine climate divisions in Wisconsin have been generated from the data provided in Huff and Angel (1992). These division-averaged rainfall frequency estimates are plotted as a family of curves describing the rainfall totals for 15 storm duration intervals (from 5 minutes to 10 days) as a function of recurrence intervals ranging 2 months through 100 years.

**INTERPRETATION:
**

For a climate division, the amount of rainfall that could be expected to be
equaled for a given recurrence interval typically increases with longer storm
durations. For example, rainfall totals in south central Wisconsin that
would have a 50-year recurrence interval range from 0.73 inches for
5-minute duration through 9.33 inches over a 10-day span. A 24-hour storm
total that would equal 6.06 inches in this division would represent a rain event
with a 50-year recurrence time.

Alternatively, a 24-hour precipitation total of 1.24 inches would have a
recurrence interval of 2-months (0.17 years), a total of 2.25 inches would have
a one-year recurrence, while a 7.06 inch or greater total would represent a once
in 100 year event. A five-day rainfall total of almost three inches (2.99
inches) could occur once in one year, while 9.36 inches would have a recurrence
interval of 100 years.

**REFERENCES:
**

Huff, F.A. and J.R. Angel, 1992: *Rainfall Frequency Atlas of
the Midwest. *Illinois State Water Survey, Champaign, Bulletin 71.

Available as a 123-page pdf file at
http://www.sws.uiuc.edu/pubdoc/B/ISWSB-71.pdf

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*Latest revision: 23 November 2007*

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*URL Address: http://www.aos.wisc.edu/~sco/clim-history/division/graphics/Rainfall_freq/rain_freq-graphics.html*