Precipitation Frequency Atlas Maps
(Central and Eastern U.S.)

These images were scanned from a copy of
TECHNICAL PAPER NO. 40
Rainfall Frequency Atlas of the United States

Precipitation Frequency Information

Precipitation Frequency is a term used in the same manner as flood frequency; as in 100-year flood. But what does this mean, one big storm every 100 years? If we had "the 100-year storm" last year, does that mean that we have to wait 99 years for the next one? Well, no, it may happen next year, or not at all in the next 100 years.

100-Year Event is an event which has a 1 percent chance of occurrence IN ANY YEAR; NOT ONE event every 100 years

Precipitation Frequency Values are used as basic design criteria for a wide variety of hydraulic structures such as culverts, roadway drainages, bridges and small dams. Current precipitation frequency studies for the continental United States are contained in studies that were completed from the early 1960s to the mid-1970s. These references provide information for durations from 5 minutes through 10 days, and for return periods of 2 years through 100 years. Furthermore, these documents provide an extreme precipitation climatology.

Scanned images for the Western U.S. can be obtained from the Western Region Climate Center.

 

Period-Event 24-Hour 12-Hour 6-Hour 3-Hour 2-Hour 1-Hour 30-Min
100-Year 100 Yr, 24 Hr 100 Yr, 12 Hr 100 Yr, 6 Hr 100 Yr, 3 Hr 100 Yr, 2 Hr * 100 Yr, 1 Hr 100 Yr, 30 Min
50-Year 50 Yr, 24 Hr 50 Yr, 12 Hr 50 Yr, 6 Hr 50 Yr, 3 Hr 50 Yr, 2 Hr 50 Yr, 1 Hr 50 Yr, 30 Min
25-Year 25 Yr, 24 Hr 25 Yr, 12 Hr 25 Yr, 6 Hr 25 Yr, 3 Hr 25 Yr, 2 Hr 25 Yr, 1 Hr 25 Yr, 30 Min
10-Year 10 Yr, 24 Hr 10 Yr, 12 Hr 10 Yr, 6 Hr 10 Yr, 3 Hr 10 Yr, 2 Hr 10 Yr, 1 Hr 10 Yr, 30 Min
5-Year 5 Yr, 24 Hr 5 Yr, 12 Hr 5 Yr, 6 Hr 5 Yr, 3 Hr 5 Yr, 2 Hr 5 Yr, 1 Hr 5 Yr, 30 Min
2-Year 2 Yr, 24 Hr 2 Yr, 12 H 2 Yr, 6 Hr 2 Yr, 3 Hr 2 Yr, 2 Hr 2 Yr, 1 Hr 2 Yr, 30 Min
1-Year 1 Yr, 24 Hr 1 Yr, 12 Hr 1 Yr, 6 Hr 1 Yr, 3 Hr 1 Yr, 2 Hr 1 Yr, 1 Hr 1 Yr, 30 Min
 

* Data Unavailable

 


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