The National Oceanic and Atmospheric Administration (NOAA) and its Storm Prediction Center (SPC) maintain the most comprehensive database of severe weather events in the United States. Every significant hail event, tornado touchdown, and damaging wind report is logged, verified, and made publicly available — often within hours of the event. For roofing contractors, this data is one of the most valuable free resources in existence.
How NOAA Collects Hail Reports
Hail reports in the NOAA/SPC database come from multiple sources. The primary contributors are trained NWS storm spotters — volunteers and professionals who report severe weather events directly to their local National Weather Service office. Additional reports come from law enforcement, emergency management agencies, and automated weather stations. Each report is assigned a location (latitude and longitude), a time, and a hail size measurement in inches.
It is important to understand that these are point reports, not area measurements. A single hail report at a specific coordinate does not mean that hail only fell at that exact spot — it means that a qualified observer confirmed hail of a certain size at that location. The actual hail swath typically extends for miles in the direction of storm movement.
Understanding Hail Size and Roof Damage
Hail size is measured in diameter and is often described using common reference objects. Hail under 0.75 inches (pea size) rarely causes meaningful roof damage on its own. Hail between 0.75 and 1.0 inches may cause cosmetic damage and is worth inspecting, but insurance claims are often difficult to substantiate at this size. Hail between 1.0 and 1.5 inches is the threshold at which most insurance policies begin to consider functional damage — this is the range where you will find the most approvable claims. Hail above 1.5 inches causes severe functional damage to virtually all roofing materials and almost always results in a full replacement recommendation.
The Difference Between Radar Estimates and Confirmed Reports
Many weather apps show hail size estimates derived from radar data — specifically from a radar algorithm called Maximum Estimated Size of Hail (MESH). MESH can be useful for identifying where large hail is likely to have fallen during an active storm, but it is an estimate, not a confirmed measurement. Insurance adjusters and contractors who rely solely on MESH data sometimes find that the actual ground-truth hail size differs significantly from the radar estimate.
Confirmed NWS storm reports, by contrast, represent actual observations by trained spotters. When you are building a case for a homeowner about why their roof needs replacement, a confirmed NWS report showing 1.75-inch hail at their coordinates on a specific date is a far stronger piece of documentation than a radar estimate.
Using NOAA Data in the Sales Process
One of the most underutilized applications of NOAA hail data in roofing sales is using it as a trust-building tool with homeowners. Many homeowners are skeptical when a contractor shows up unsolicited after a storm and tells them their roof is damaged. Showing them a printed or digital NWS storm report — with the date, time, location, and confirmed hail size — immediately shifts the conversation from “this contractor is trying to sell me something” to “this is a documented weather event and I should take it seriously.”
THOR Storm Mapper displays this data in a format that is easy to share with homeowners directly from your phone. The combination of a visual impact map and the underlying NWS report data gives contractors a credibility advantage that competitors relying on word-of-mouth or news reports simply cannot match.
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