SPC Storm Reports: What They Are & How to Use Them

Published 2026-07-14 · Updated 2026-07-14

SPC (Storm Prediction Center) storm reports are vital pieces of information that document severe weather occurrences like hail, high winds, and tornadoes, often submitted by trained spotters or emergency managers.

Understanding SPC Storm Reports

When severe weather strikes, confirming its impact can be challenging. One of the most valuable resources for understanding past severe weather events is the collection of Storm Prediction Center (SPC) storm reports. These reports provide a ground-truth perspective on what actually happened during a severe storm.

What are SPC Storm Reports?

SPC storm reports are real-time submissions of observed severe weather events, including hail, damaging winds, and tornadoes. They are often collected from a network of trained weather spotters, emergency management officials, law enforcement, and sometimes even the public. These reports are crucial because they offer specific details about the location, type, and severity of an event, which might not always be captured by radar alone.

For hail, reports typically include the observed diameter (e.g., "1.00 inch hail"). For wind, they might detail estimated gust speeds or describe the observed damage (e.g., "trees down," "power poles snapped"). Tornado reports include the location and sometimes an initial damage assessment.

These reports are compiled by the SPC, a branch of the National Weather Service (NWS) that forecasts severe convection. While they are a critical source of information, it’s important to remember they are reports of observations, not official NWS warnings, and their accuracy can vary depending on the observer and conditions.

How StormAuditor Uses SPC Storm Reports

StormAuditor integrates SPC storm reports into its detailed historical weather records, especially for our Hail Explorer and Wind Explorer tools. These reports serve as a key component in our methodology because they provide observed conditions on the ground.

For example, in our StormAuditor Hail Estimate v2 (SAHE-2), SPC hail reports are used to corroborate radar-derived estimates from MRMS MESH (Maximum Estimated Size of Hail) data. If an SPC report indicates 1.75-inch (golf ball size) hail near a property, it strengthens the estimate of severe hail in that area.

Similarly, for our StormAuditor Wind Estimate v2.7 (SAWE-2.7), SPC wind reports, which might detail fallen trees or estimated gusts, help to contextualize daily peak wind readings from weather stations and provide additional evidence of severe wind conditions in a location.

When you request a property-level historical weather report at /address-lookup, StormAuditor cross-references your address with nearby SPC storm reports. This allows us to provide a more comprehensive picture of the severe weather activity in your area on a given date during our DOL research workflow.

Limitations

While SPC storm reports are incredibly valuable, they do have limitations that StormAuditor accounts for:

  • Spatial Gaps: Reports are only generated where someone observes and reports an event. There can be significant gaps in coverage, meaning severe weather might occur without being reported.
  • Timing: Reports provide a snapshot, but the precise timing might not be down to the minute. The reported time is typically when the observation was made or the event occurred.
  • Observer Bias: While many reporters are trained, different observers might estimate hail size or wind damage slightly differently. This can lead to variability in report accuracy.
  • Under-reporting: Not all severe weather is reported, especially in rural areas or during overnight hours. Therefore, the absence of an SPC report does not mean severe weather didn’t happen.

StormAuditor addresses these limitations by integrating SPC reports with multiple other data sources, including NWS severe weather warnings, radar-derived products like MRMS MESH, and station-based wind data to build a more complete and robust estimate of weather conditions. This multi-source approach helps to mitigate the individual weaknesses of any single data source. For more details, see our /limitations page.

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FAQ: SPC Storm Reports

Q: What's the difference between an SPC storm report and an NWS warning?

A: An NWS severe thunderstorm or tornado warning is an official alert issued by the National Weather Service indicating that severe weather is imminent or occurring in a specified area. An SPC storm report is an observation of a severe weather event that has already occurred, providing ground-truth confirmation. StormAuditor uses both in its analysis.

Q: Do all severe weather events generate an SPC report?

A: No. While many do, especially in populated areas or where spotters are active, some severe events go unreported. This is why StormAuditor uses multiple data sources—to provide the most complete picture possible, even when specific reports are absent.

Q: How accurate are hail sizes in SPC reports?

A: Hail sizes in SPC reports are typically visual estimations by observers. While many observers are trained, estimations can vary. For context, 1.00" is quarter-sized, 1.75" is golf ball-sized, and 2.00" is hen egg-sized hail. StormAuditor combines these reports with radar-derived data for a more refined estimate.

Q: Can I use SPC reports to prove damage?

A: SPC reports indicate what severe weather was observed in an area. While they are a strong indicator of severe conditions, StormAuditor cannot prove damage causation. We provide the weather context; causation is determined by qualified damage assessors. For more information, please see our /sample-report and /limitations pages.

Q: Where can I see raw SPC storm reports?

A: The Storm Prediction Center's website offers access to raw storm reports and archives, as does the Iowa Environmental Mesonet (IEM) archives. These are public data sources StormAuditor uses. https://www.spc.noaa.gov/climo/online/ and https://mesonet.agron.iastate.edu/