One headline says that the recent winter storms in Vancouver were predicted “almost exactly”. Another headline, 4 days later, says that almanac predictions for the east coast of the U.S. were entirely wrong because springlike conditions occurred when one to two feet of snow had been predicted.
What is going on here? Can we trust an almanac to tells us what the weather will be like, as much as a year in advance?
It turns out that there are many almanacs, with some competing head-to-head. In the U.S., The Old Farmer’s Almanac started in 1792, while the younger rival The Farmers Almanac started publishing in 1818. These almanacs have had a long time to perfect their prediction methods and get things right. But, alas, time has not helped.
A recent article by Dr. Karen Stollznow in Skeptic Magazine provides a nice summary of the history and techniques used in making weather predictions:
The Farmer’s Almamac forecaster, who is only known by the mysterious pseudonym Caleb Weatherbee, uses a “top secret mathematical and astronomical formula, that relies on sunspot activity, tidal action, planetary position and many other factors.” These methods seem to be the “11 herbs and spices” of weather forecasting.
The other almanac uses a similar, secret formula. But how well do they work?
A study conducted in 1981 found that the Old Farmer’s Almanac was no better than chance at predicting the weather for 32 locations around the US. A careful reading of the predictions also shows that they are vague, generalized, and strongly tied to the seasonal averages. Much like astrology, almanacs are relying on the Barnum effect, where people will consider general statements to be very accurate if they believe the statements are tailored just for them (or their local weather).
Almanacs do offer more than weather forecasts, and that might explain some of their appeal:
Almanacs offer an awkward mix of science and superstition. They present factual astronomical information about moon phases, alongside spurious astrological claims. They still offer handy hints, gardening tips and recipes for comfort food, and teach you how to clean the toilet with Coca-Cola and keep fleas away from your dog naturally. Sticking to their roots of prediction, they provide the “best days” to cut hair to increase growth, to quit smoking, apply for a loan or shop for clothes.
So far, nobody can predict the weather far in advance, and certainly not an almanac. But maybe it can tell me when to get my hair cut.