Start by using NOAA’s data
The best resource we've found for rainfall intensity data is NOAA's Hydrometeorological Design Studies Center Precipitation Frequency Data Server.
Start by choosing your state from the U.S. map. Depending on your state, there are two different step-by-step processes. Blue-colored states allow you to search the database, and provide easy-to-read data tables. Gray-colored states require you to determine the value for your site by reading isopluvial maps. We’ll explain both, step by step.
