Old Farmer's Almanac: Long range weather forecasts

How The Old Farmer's Almanac Predicts The Weather

We derive out weather forecasts from a secret formula that was devised by the founder of this Almanac, Robert B. Thomas, in 1792. Thomas believed that weather on Earth was influenced by sunspots, which are magnetic storms on the surface of the Sun.

Over the years, we have refined and enhanced that formula with state-of-the-art technology and modern scientific calculations...

...our results are almost always very close to our traditional claim of 80 percent.