grayscale photography of thermometer on wall

By Herb Fischer

One of the reasons it is so hard to get early-season snowfalls in the Northeast and mid-Atlantic is that the dew-point temperatures are still so high. Especially anytime a storm cuts to our west and north, the dew point temperature sometimes surges as high as the 50s and 60s right through November–almost summertime levels!

In any given air mass, the dew point is the point at which the temperature on your thermometer would have to fall in order for the air to get saturated. In the wintertime, if the dew point is 31 degrees before a storm arrives, it probably won’t snow, because the incoming storm would soon make the atmosphere warmer and wetter, and raise the dew point a few degrees, even if the incoming storm slides to the east and south.

Sometimes in a tropical rain forest or summer in South Florida, the dew point may get as high as 82 degrees! Can you imagine that? The air is so humid, that the temperature cannot fall lower than 82 degrees!

I have found that the best surprises for snowstorms come late in winter, even early spring. Sometimes the strong March sun will heat up the surface air that is still cold and dry from the long winter. The temperature may spike into the 60s on a sunny day, but the dew point is depressed as low as the teens!

As long as that air mass remains that dry, I am never surprised if a wet snow falls the next day with an incoming storm, with a favorable storm track!

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