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 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 sums those reports 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 minimum size that NOAA classifies as "hail" in storm reports. Below this size, the event is typically recorded as ice pellets, not hail.

1.00 inch — The NWS "severe hail" threshold. A storm report at or above this size triggers severe thunderstorm warnings. 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 maintains two related tables. The storm_reports table stores individual LSR entries — each row is one observation, with date, county, size, and coordinates. The hail_events table aggregates those individual reports into annual county-level counts. The top-10 county list and the state-year tables in our research posts all come from the hail_events aggregate.

This structure means that "777 events in County FIPS 08041" represents 777 individual storm reports — 777 separate occasions over 11 years when a spotter in that county recorded hail at or above 1.0 inch. That context matters: it is not 777 unique hailstorms, because a single storm can generate multiple spotter observations across the same county on the same day.

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. This is the threshold that triggers severe thunderstorm warnings when hail is observed or forecast.

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 verified contractor coverage in our database. If it does not, we flag it as a coverage gap and prioritize outreach to qualified contractors in the area.