On Sunday, there were reports of snowfall in Philadelphia along with wind, thunderstorms, and extremely high temperatures. This happens during a week of exceptionally unusual weather in the northeastern United States.
A brief hailstorm touched down at Philadelphia International Airport on Sunday afternoon. The National Weather Service in Mount Holly, New Jersey, recorded the observation as snow. Official guidelines state that hail is considered frozen precipitation, placing it in the same category as snow, sleet, and graupel.
This small notation in the daily climate report might have gone unnoticed if not for a pair of social media posts by the weather service on Monday morning.
At 2:12 a.m. on Monday, the weather service posted on X, explaining that the small hail was reported as a “trace” of snow. This led to a record event report stating, “A record snowfall of a trace was set at Philadelphia, PA yesterday.
Thirteen further incidents of thunderstorm hail in June, July, and August that resulted in reports of a trace of snow were found by the meteorological service.
When broadcast meteorologists nationwide inquired about reporting hail as snow, the responses from weather service offices varied. In Greenville-Spartanburg, South Carolina, the weather service office stated on Wednesday that it is common practice to classify hail as a trace of snow in their climate summaries. On the warmest day ever recorded at the station, there was a trace of “snow” according to historical climate data for the Greenville office. On July 1, 2012, the temperature hit a record high of 107 degrees, but hail observed that afternoon was reported as “snow.”
Weather forecast offices in Dallas/Fort Worth and Tallahassee informed meteorologists that they do not report hail as snow.
Jim Zdrojewski, a climate services data program analyst at weather service headquarters, is unsure when the practice of recording hail as snow began. This is how we’ve been recording it for a very long time, to ensure the continuity of the climate record.
The reporting forms include separate columns for precipitation and snow, with an additional column noting if the “snow” was actually hail.
Zdrojewski noted that he could not speak for all 122 field offices and their individual practices. “We provide the instructions,” he said.
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To preserve consistency in their local climatic records, offices that have never recorded hail as snow are welcome to go on with that practice. Furthermore, he highlighted the distinction between “recorded” and “reported.”
Individual offices have some flexibility in how they report events, especially in their social media posts. Zdrojewski would not rule out bringing up the subject when he spoke with managers of regional climate programs in a planned teleconference on Wednesday afternoon. We welcome recommendations from you on how to make things better.