NC Probable Maximum Precipitation Study and 
Evaluation Tool (May 2025)

This study provides gridded Probable Maximum Precipitation (PMP) values and associated Temporal Distributions covering the entire state of North Carolina and immediate surrounding regions adjacent to the state that also provide runoff into drainage basins within North Carolina. The PMP grid domain uses a spatial resolution of 0.025 x 0.025 decimal degrees (approximately 2.3-square miles). 

The study is based on the most current practices used for defining PMP, including comprehensive storm analyses procedures, extensive use of geographical information systems (GIS), explicit quantification of topography and coastal effects, updated maximum dew point and sea surface temperature climatology for storm adjustments, and improved understanding of weather and climate related to extreme rainfall in the region. 

The study also included data collected over a longer period of storm records, in which a total of 91 storms from the past 150 years were considered. Recent storms Hurricane Helene and Tropical Cyclone Eight that severely hit parts of NC in September 2024 were also considered in the study. 

Results of this NC PMP study will supersede those provided in Hydrometeorological Reports (HMRs), including HMRs 33, 51, 52, and 56.
 

Deliverables from the PMP study are available for download below

Disclaimer

The deliverables generated by the North Carolina Probable Maximum Precipitation Study (“Study”) are provided on an “as-is” basis and are intended to supplement but not replace all existing statutory and regulatory requirements.

The North Carolina Department of Environmental Quality (“DEQ”) assumes no responsibility or liability for any use or misuse of the data, outputs, or analyses retrieved from the Study deliverables. All results and conclusions of the Study are based on data from national, state, and local data sources and have been developed using best professional judgment to ensure accuracy and completeness.

The results generated by the Study reflect the best available data, and all data sources and methodologies are documented on the Study website or the respective data owners' platforms. While the Study incorporates historic and current data, it cannot predict future conditions—such as spatial changes, risks, environmental shifts, or other variables—with absolute certainty.

No warranties, expressed or implied, are provided regarding the accuracy, completeness, or interpretation of the data. Use of the Study deliverables is at the user’s own risk. In no event shall DEQ or its collaborators be liable for any direct, indirect or incidental damages arising from the use or application of these Study deliverables.

By accessing and using any of the Study deliverables, users acknowledge their sole responsibility to verify the information provided and to take all steps necessary to ensure proper use and understanding of these products and that all information is being properly interpreted and applied.

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