Severe thunderstorm warning
Definition
- Related pages
- 5
- Last revised
- 23 August 2026
A severe thunderstorm warning is issued by a forecast office when radar, a spotter or both indicate that a storm producing hail at or above the severe criterion, wind at or above the severe criterion, or both, is happening or is about to inside an area the forecaster draws. The warning names the area as a polygon, gives an expiry time, and, since offices began tagging warnings, states the largest hail and strongest wind the forecaster expects. A storm producing a tornado gets a tornado warning instead; a storm below the criteria gets none.
A warning is a forecaster's judgement made before or during the event, which is its value and its limit. It attests that at issue the office considered the storm severe and expected it to cross the polygon, a strong statement about the storm's existence and path. It does not attest that hail fell at any point inside the polygon, that the tagged size was reached anywhere, or that a property near the edge was inside the storm. A warned storm with no reports was expected; a reported storm with no warning was not.
In this archive a warning is its own kind of evidence, an official warning, filed on the observed side of the line because an office issued it at a time for a place. It counts as one independent kind beside ground observations and radar detections when a finding is graded, and it never draws a hail swath, because a tagged size is what was expected rather than what was found.
In the report
How the document prints it
In the report a warning appears in the record table as a row with its date and time, its type, its tagged hail and wind where the office gave them, and its source; it has no distance, because a polygon either contained the address or did not, and the row says which. A warning that contained the address is classed as contributing evidence rather than primary, since containment is a stronger statement than proximity and a weaker one than a measurement at the place. Its citation under Sources and method says that only polygons geometrically containing the address were searched.
From the record
23 Aug 2026
The criteria a warning is issued against, and when the record last met them
- Severe hail criterion
- 1.00″
- Severe wind criterion
- 58 mph
- Largest measured hail, most recent severe day
- 1.75″
- Strongest measured wind, most recent severe day
- 75 mph
Hail last reached the 1.00″ criterion anywhere on record on 23 August 2026, from 40 hail reports; a measured gust last reached the 58 mph criterion on 23 August 2026, among 135 wind reports. A warning says a forecaster expected those criteria inside a polygon; the reports are what was found.
Measured Detected, not measured
The page these figures come fromRelated
The terms this page uses and the guides that go further. Each is shown against its own example from the record.
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Term
Warning polygon
The area a forecaster draws when issuing a severe thunderstorm or tornado warning, inside which the warning applies and outside which it does not.
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Term
Hail size
The diameter of the largest hailstone at a place, reported in inches or by the named object on the spotter chart it was compared with.
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Term
Peak gust
The highest wind speed recorded over a brief interval, a few seconds, at a station or by an observer during a storm or a day.
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Term
Independent source
A record-keeping route by which a storm reached the archive, counted once however many rows it produced, so that agreement between routes can be measured.
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Guide
How far away a hail report can be and still count
A hail report is a point: where a person stood, or where a radar placed a signature. A property is another point. The distance between them is the first thing a reader checks and the first thing a reader misreads. This guide states what a distance establishes, how the report bands it, and why a record filed to a county cannot be measured from at all.
Sources
The primary references. Each opens on the agency's own site.
The glossary defines the word. The report is what uses it.
Everything above is definition: what the word means in the document, and what it does not. None of it says what reached one roof.
Run the address and the archive is searched at the property: the storm, the date, the measured size, the distance and bearing from the roof, and the federal record each figure came from, in a document that states its own method. About a minute.
How this page is made
- The text
- Written by the editors and last revised 23 August 2026. It explains the record and how the report reads it; it contains no figure of its own.
- The example
- Drawn from the archive when the page was compiled, 24 August 2026, and rebuilt daily as the record deepens. Every figure in the panel marked From the record is computed, not written, and links to the page it came from.
- Measured and detected
- A report from a person or an instrument is measured. A radar-derived size is detected, not measured, and is marked as such, here and in every document we issue. The two are never added together.
- What this is not
- A definition of a word the report uses. It is not a report on any property, and it states no opinion about one. The coverage page states what the record holds, by kind and by year.
About this record
Everything here is reproduced from public federal and volunteer weather records, as the agencies and observer networks that publish them released it. Titan Weather compiles the record; it does not observe the weather, and it is not affiliated with any source it cites.
No archive holds everything. Storms cross places where nobody is standing, instruments and spotters cover some areas better than others, sources revise their records, and recent reports can take weeks to arrive and settle. Where this page shows nothing, nothing was found in the sources searched, within the period and area it states. That is not a finding that no weather occurred.
These pages describe the public record near a place or on a date. They do not establish what reached any particular property, and nothing here is insurance, legal or engineering advice.