In the US, the sport of long-range weather prediction is dominated by two annual publications, the Farmer’s Almanac (founded in 1818) and the rival Old Farmer’s Almanac (1792). These confidently make detailed weather predictions for the forthcoming year.

Both almanacs are bestsellers with millions of readers who take them seriously. And they have both caused some consternation by predicting a severe winter ahead.

Scientific meteorologists are more cautious about long-range forecasting. Many interacting forces make for unpredictable outcomes, so they express their forecasts in broad probabilities.

The founders of the two almanacs developed their own systems from beliefs that were fashionable at the time, but are no longer scientifically accepted. The Old Farmer’s Almanac predictions are based on solar activity and prevailing weather; these days satellite data is also factored into the calculation. Their newer rivals have a formula combining solar and lunar activity and the movements of the planets. The details of both methods are kept strictly secret.

The almanacs’ winter predictions differ considerably in detail, with the Farmer’s Almanac suggesting a “polar coaster” of highs and lows worst in the east. Whatever happens, it is likely that successes will be remembered and failures ignored. This human tendency, known as confirmation bias, may do more to keep almanacs in business than the reliability of their secret formulae.



