(CNN) -- The story goes that, in 1815, Old Farmer's Almanac founding editor Robert B. Thomas was interrupted by a boy wondering what to put down for the weather forecast of July 13, 1816.
In some versions, Thomas is ill with the flu. In others, he's simply preoccupied with other work. Whatever the reason, the entry for that day -- perhaps Thomas' suggestion, perhaps one from an impish interloper -- was supposedly "rain, sleet and snow." In July.
It so happened that 1816 was "the year without a summer," thanks to the eruption of Mount Tambora, and it did, indeed, sleet and snow that season, even in July. The forecast is alleged to have made the almanac's reputation.
It's a nice story, though even the almanac itself is skeptical of its truth.
Nevertheless, the almanac has become a closely watched predictor of weather, particularly winter weather. It released its forecast for 2015-16 over the weekend, with expectations of bitter cold, December snow in the Pacific Northwest, above-average precipitation in New England and icy conditions in the South.
The forecast immediately started trending, as it seems to do every year. But does it have any validity?
Dave Hennen, senior meteorologist and executive producer for CNN Weather, says it should be taken with a grain of salt -- and not necessarily road salt.
"It's difficult enough to do a five-day forecast," he said. "We're really good at the day of and the next day, (and) we're better at temperature a ways out than precipitation. But to forecast out that far in advance ... even the science behind our long-range forecasting is sometimes not that solid."
From a 'secret formula'
The 224-year-old almanac, with its kitschy cover and homespun advice, does say that it's "useful, with a pleasant degree of humor." The heart of the book, says editor Janice Stillman, is its calendar of the heavens, complete with various astronomical tables.
"From that springs all the rest of the content," she said in a phone interview from the almanac's offices in Dublin, New Hampshire.
And the weather? According to its website, the almanac bases its forecasts on a "secret formula" (yes, just like Coca-Cola) that is "locked in a black box."
The formula itself has dollops of science to go along with its historical methods.
"Over the years, we have refined and enhanced that formula with state-of-the-art technology and modern scientific calculations," the site says. "We employ three scientific disciplines to make our long-range predictions: solar science, the study of sunspots and other solar activity; climatology, the study of prevailing weather patterns; and meteorology, the study of the atmosphere."
In press materials, the almanac claimed 96.3% accuracy for its "2015 predictions of a bleak and biting winter." Stillman says the figure is based on an analysis of the almanac's forecasts of its 16 regions on a monthly basis.
Meteorologists and weather experts don't buy it.
"Both (the Old Farmer's Almanac and its competition, the Farmers' Almanac) claim high accuracy rates (around 80 percent) but have never published evidence backing them up. They lack transparency and keep their methods 'closely guarded,' " wrote the Washington Post's Jason Samenow in 2013.
Added Dennis Mersereau of Gawker's "The Vane," "The Old Farmer's Almanac is to meteorology what astrology is to astronomy."
For his part, Hennen observes that the huge El Niño event anticipated this year, for example, should produce a great deal of precipitation in the drought-parched West, though the Old Farmer's Almanac says the region will remain dry.
"The meteorology forecast is much better because it has (more) science behind it than what the Old Farmer's Almanac has," he said.
Will it be wrong?
Stillman stands by the almanac's forecast.
"We are not really expecting that to happen," she says.
Last summer, she observes, there were expectations an El Niño would form, but the almanac thought it would be neutral to weak. The almanac's meteorologist, Michael Steinberg, believes that the same will be true this year.
Not that the almanac would mind being wrong, says Stillman: "There would be so much more upside for so many more people," she says.
Even if it is wrong, people may not remember the specifics. Hennen points out that the Maine-based Farmers' Almanac -- the Old Farmer's Almanac's rival -- missed the forecast for the New Jersey-based Super Bowl in 2014, predicting a messy "Storm Bowl." The actual weather? Close to 50 degrees at kickoff.
(The Old Farmer's Almanac, which also predicted rough weather that day, noted in a comment response on its website that it was "on trend.")
After all, more than two centuries into its run, there's still a solid demand for the Old Farmer's Almanac. Stillman says that about 3 million copies are printed, and the title just passed 1 million fans on Facebook. Whether for entertainment or information, people read it for everything from gardening tips to holiday lists. (And, yes, weather forecasts.)
"It's a symbol and manifestation and perpetuation of country values in life," says Stillman.
Even Hennen is more amused than offended by the attention it brings. He tips his hat -- or should that be a nice wool toque? -- to the almanac's longevity, if not its methodology.
"(Long) before meteorologists were putting out their winter predictions, the Farmer's Almanac has been doing this," he said. "I think people remember that. Nowadays, even meteorologists are putting out outlooks for 'is it going to be a busy hurricane season?' 'Is it going to be a bad winter?' I think we're just kind of new to the game, whereas the Farmer's Almanac has been doing it forever."
By Todd Leopold
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