What a NOAA Hail Report Really Tells You

Most homeowners encounter a NOAA hail report indirectly, through a news headline, a text alert, or a call from a roofing contractor who tracked the storm data and knocked on doors in the affected neighborhood. But the underlying report contains more information than a headline conveys, and knowing how to read those fields helps you decide whether your roof actually needs attention after a storm.

The Anatomy of a Local Storm Report (LSR)

NOAA's Local Storm Reports (the Storm Prediction Center publishes daily hail reports) are issued by regional National Weather Service offices when a trained spotter, law enforcement officer, or automated sensor observes a qualifying weather event. For hail, the relevant fields are:

event_date: The date and time (UTC) the hail was reported. Reports sometimes arrive hours or even a day after the event, depending on when a spotter submitted their observation. The event time is the observation time, not the processing time.

location: A text description of where the observation occurred, typically an intersection, landmark, or distance from a named town. This is human-readable but not precisely geocoded in every report.

county and state: The county and state FIPS identifiers. These are what our database uses to aggregate events at the county level. Individual reports map to a county; our hail_events table counts hail records from the NOAA Storm Events Database by county and year.

lat/lon: Where available, the report includes latitude and longitude coordinates. Not all historical reports contain precise coordinates, particularly older entries.

size_in: The measured or estimated hail diameter in inches. This is the field that drives most practical decisions.

comments: Free-text observations from the spotter. These often contain context that the structured fields cannot, "hail covered the ground," "windshields cracked," "stripped leaves from trees." Reading the comments on a report gives a richer sense of the event's severity than size alone.

Size Thresholds That Matter

Not all hail in an LSR is created equal. There are three size thresholds that have practical significance:

0.75 inches, The smallest hail the National Weather Service enters in Storm Data: all reports of hail 3/4 inch or larger are entered (NWS Instruction 10-1605).

1.00 inch, The NWS "severe hail" threshold: a storm capable of producing hail an inch or larger counts as a severe thunderstorm. This is the minimum size our storm_reports table captures for tracking purposes. The 388 reports in our July 1–14, 2026 snapshot are all at this threshold or above.

1.75 inches, Golf ball size. This is the informal industry threshold above which roof damage is considered likely rather than merely possible on standard asphalt shingle installations. Our snapshot showed 81 of 388 reports at or above this size in that two-week period.

From Reports to Our Database

PickARoofer keeps two separate tables. The storm_reports table stores individual daily hail reports from the NOAA Storm Prediction Center, one row per report, with date, county, size, and coordinates, at 1.0 inch or larger. The hail_events table holds annual county-level counts built from the NOAA Storm Events Database (2014 to June 2026), where hail of 3/4 inch and larger is entered. The top-10 county list and the state-year tables in our research posts come from hail_events.

This structure means that "869 events in El Paso County, Colorado" represents 869 hail records in the Storm Events Database for that county from 2014 to June 2026. That context matters: it is not 869 unique hailstorms, because a single storm can generate more than one record in the same county.

What Size Means for Roofing

Size is the most practically useful field in an LSR for anyone assessing roof damage potential. Hail that barely meets the 1.0-inch threshold is unlikely to cause immediate visible damage to a well-maintained roof in good condition, though it may accelerate granule loss over time on older shingles. At 1.75 inches and above, functional damage, bruising through the shingle, granule stripping that exposes the underlying mat, becomes a realistic outcome on most residential roofing materials. Size above 3 inches generally signals that a qualified inspection is warranted regardless of visible signs from the ground.

Frequently Asked Questions

What is the NWS threshold for severe hail?

The National Weather Service classifies hail as severe at 1.00 inch in diameter or larger: a storm capable of producing hail that size is a severe thunderstorm.

What does 1.75 inches mean for roof damage?

1.75 inches (golf ball size) is the informal threshold at which roof damage is considered likely on standard asphalt shingle roofs. Below this size, damage is possible but less predictable; above it, a professional inspection is generally advisable.

Are NOAA storm reports always accurate?

LSRs are observational records, not measurements from calibrated instruments in most cases. Spotter estimates of hail size can vary, and not every hailstorm is observed by a trained reporter. The database provides the best available spatial record of hail events, but it should be understood as an observational dataset with inherent variability.

How does PickARoofer use storm reports to identify contractor needs?

When a significant hail event is recorded in a county, we check whether that county has adequate contractor coverage in our database. If it does not, we flag it as a coverage gap.

Sources and data notes

• NOAA Storm Prediction Center, storm reports archive
• NOAA NCEI Storm Events Database
• NWS Instruction 10-1605, Storm Data Preparation (hail reporting rules, size guide)
• National Weather Service: thunderstorm safety (severe thunderstorm definition)
• U.S. Census Bureau: FIPS / ANSI code lists

Data: NOAA Storm Prediction Center daily hail reports (storm_reports, 1.0 inch or larger) and NOAA NCEI Storm Events Database (hail_events, 2014 to June 2026), processed by PickARoofer; hail_events loaded 2026-10-06, source links last rechecked 2026-09-24.

Sources

• Storm Prediction Center publishes daily hail reports (spc.noaa.gov)
• NWS Instruction 10-1605 (weather.gov)
• severe hail (weather.gov)
• NOAA NCEI Storm Events Database (ncei.noaa.gov)
• U.S. Census Bureau: FIPS / ANSI code lists (census.gov)

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