Metro

Who’s behind measuring Boston’s official snow total?

If that moment comes when Boston breaks its record for snowfall — we’re less than 2 inches away — this is how it will go down.

First, it will snow.

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Next, a man will stick a ruler into that snow at Logan Airport.

If the snowfall exceeds 1.9 inches, that man will then bear witness to a landmark moment in the history of Boston.

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He will be the only witness.

The Ruler of the Logan Ruler does not do interviews. He does not do photos. At his request, the National Weather Service won’t even release his name.

But for nearly two decades, this mysterious volunteer has been responsible for the last hand measurement used in the recording of the “official” Boston weather: the snowfall total at Logan Airport.

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Since the 1930s, Logan has been the official observation location for city weather. Until the mid-’90s, its weather station was staffed round-the-clock by observers recording things such as temperature, precipitation, and wind speed. But when the National Weather Service moved its regional headquarters to Taunton, the Logan station became fully automated. Almost.

It is impossible to accurately measure snowfall remotely, so when the flakes start falling, the Ruler of the Logan Ruler will make four trips per day to the airport — at 7 a.m., 1 p.m., 7 p.m., and midnight — and stick a ruler into the snow at various points to come up with an average accumulation.

The ruler is 40 inches long, aluminum, with a black handle on top that makes it easier to maneuver. The only major difference between this ruler and the one in your junk drawer is that it measures in tenths of an inch.

Right now, those tenths of an inch matter because Boston is creeping toward its snowfall record. After a light mix that fell Tuesday night into Wednesday, the city snowfall total — which is measured from July 1 to June 30 — was 105.7, just shy of the record of 107.6 set in 1995-1996.

After the huge right hooks Mother Nature has thrown at us all winter, it feels a tad undignified to nickel-and-dime our way to a razor-thin win. But in a winter that has been routinely described as the “worst ever,” this would at least make it official.

But there is a problem with breaking “all-time” records for weather. The most glaring is that we have only been regularly logging weather for a relatively short stretch of human history, so records come with the caveat of “in recorded history.”

But within that, there is a second problem involving the methods used to make measurements. If the method changes in any way, or the location of the measurement moves, so, too, does the definition of “all-time” record.

In Boston, the first “official records” date to 1870, when Sergeant S.E. Cole and privates Black and Huneke of the US Army Signal Service made the first official Weather Bureau observations at the Old State House at 8 a.m. on the first of November. It was a crisp 44 degrees.

The measurement location moved a couple times — to Court Street, and then to the corner of Milk and Devonshire streets — until 1884, when it settled at the Old US Post Office and Courthouse, where it remained for 45 years. From there, it bounced around a few more times before settling in for its long run at Logan.

For decades, weather observers at Logan measured snowfall totals on a bench surrounded by hedges. But since the staff moved to Taunton and the measurements were left to a volunteer observer, the approach has been to use a variety of measurements to attempt to find a representative average, said Bill Simpson, a spokesman for the National Weather Service office in Taunton.

Simpson said that does not mean the current march on the record should be viewed with an asterisk. “You just have to word it correctly. I like to say ‘most snowfall in recent recorded history.’ ”

In other ways, all snowfall records need to be viewed with an asterisk because they have always relied on the human eye.

“Measuring snow is kind of political at times, and a lot of people don’t want to get involved in it because it’s such a subjective thing,” Simpson said.

There are thousands of people who send in snowfall totals to the National Weather Service after a big storm, and Simpson said they do a lot of quality control trying to sort out which numbers can be trusted.

“A lot of people go for the highest snowfall so they can make the Weather Channel,” Simpson said. “We want a representative number, which requires skill and honesty.”

Before Boston began logging its “official” records, there were many individuals who kept private weather records, going as far back as Paul Bradley, the chief justice of Massachusetts, and John Winthrop, a Harvard professor, in the 1700s. But the National Weather Service said our current snowfall can only be judged accurately against the records kept since the 1870s, when the Weather Bureau, and later the National Weather Service, began its unbroken string of daily recordings.

“But even then, did people really understand how important snowfall was?” Simpson asked. “We hope they did it accurately, but that was over 100 years ago, before any of us were born.”

The National Weather Service trusts the accuracy of the Ruler of the Logan Ruler. And it has no problem with his desire for anonymity because, frankly, it’s not easy to find someone willing to go out four times a day in the worst weather to stick a ruler into the ground, Simpson said.

“This guy is very good, and very committed,” Simpson said.

He is also very shy. There have been many requests to interview him over the years, especially this year, but he has always declined.

So if that moment comes when we make it official, it will be, for a little while at least, a private party.

How much snow falls in March, April, and May

Boston-area snowfall totals for March, April and May by year

DATA: National Weather Service

Globe Staff

Billy Baker can be reached at billy.baker@globe.com. Follow him on Twitter @billy_baker.
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