Extreme precipitation events bring the potential for billions of dollars in losses from flooding and property damage, while endangering the lives of those who reside in affected areas.  Knowledge of the expected frequency and magnitude of extreme precipitation events is important for use by engineers when designing structures and facilities to protect against these potentially catastrophic occurrences.


Wilks and Cember (1993) produced at atlas of precipitation extremes for the Northeast U.S., regionally updating the widely used atlas of precipitation extremes for the U.S. produced by Hershfield (1961). Using improved methods and three additional decades of data, Wilks and Cember produced a regional reference for engineers that could be applied with more confidence in New York and other states in the Northeast U.S.


A new atlas has been created for New York that uses methods similar to Wilks and Cember (1993) and McKay and Wilks (1995), while taking advantage of an additional decade of observed precipitation events.  This atlas presents the extreme precipitation amounts that correspond to various accumulation periods (24-hr, 18-hr, 12-hr, 6-hr, 3-hr, 2-hr, 1-hr) and recurrence intervals (1-yr, 2-yr, 5-yr, 10-yr, 25-yr, 50yr, 100-yr).  Along with the typical return period analysis, the influence of snowmelt on these extreme precipitation return period amounts were assessed. Additionally, the probabilities of exceeding return period amounts in different regions of the state during different weeks of the year were determined, as were the probabilities of observing various numbers of consecutive days without precipitation.