Methodology

How a report is built, in plain terms.

Sources. NOAA MRMS radar (1-km grid, measured hail size), NOAA Storm Events, SPC storm reports, NWS Local Storm Reports, and CoCoRaHS volunteer hailpad measurements.

What makes the report. A date appears only when hail is measured at or near the structure — at the address, within one mile, or one inch or larger within three miles. Distant storms don't pad the report.

Confidence. Every date carries a percentage reflecting the measured historical rate at which days with the same evidence profile verified as at-property hail — combining radar strength at the address, hour-by-hour storm-track proximity, and ground observations.

Limits, stated plainly. Radar-derived size is an estimate, not an observation; close-range radar history begins October 2020; earlier dates are documented from official storm reports.