Does a warm fall mean a snowy winter? What the numbers tell us for the snow forecast

Weather Blog

ROCHESTER, NY – There is a deep desire to prescribe what a winter will be like based on the previous summer and fall, but a lack of data to support it. Only large and general trends have started to emerge because of climate change. 

October 2021 was top ten warmest going back to 1950, and that warmth could bleed into winter. This is something meteorologist and climate specialist Dr. Jeff Masters says will happen more often in the decades to come. 

“The amount of time that we’re going to experience snow and freezing temperatures has gone down,” said Masters. “The frost free period has gone up by over a week over the past 30 years.” That pushes back the start of winter as the climate warms, but when winter gets going, Masters says snowstorms could be stronger than in the past. 

“When it does snow, you can get heavier snows because the lakes now are not frozen as long, which means the lake-effect snows can kick in and give you more intense lake-effect snowstorms,” said Masters. 

Rochester averages about 100 inches of snow and it varies wildly with seasons getting less than 70” to seasons with over 130”, so we searched for a correlation between past temperature and precipitation with seasonal snowfall. 

The methodology here was to take every seasonal snowfall since 1970 and plot it on the y-axis. We then change the x-axis to certain variable, starting with that year’s October temperature. We then calculate the r-squared value to see if there is any relationship. It depends on the certain field, but an r-squared value generally above .75 would be considered a good correlation. 

The correlation was .0005, or less than one half of one percent. While this does not mean there is no correlation, it is evidence that a relationship between the two is very unlikely. 

No correlation was found when plotting October precipitation as well. When comparing a summer temperatures and precipitation to seasonal snowfall, no correlation emerged. The same sign emerged when looking at fall temperature and precipitation. 

The only data that we found that was barely there a seven percent correlation that a colder November could mean more snow, but more data could help in coming to a conclusion. 

While we don’t have any evidence of  summer or fall to predict the winter, we could use Lake Ontario, as it’s one of the warmest it’s ever been in November. The last time it was this warm was the year 2000, when we got over 130 inches of snow. 

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