Geocentric Science

During the winter, cold dry (very low relative humidity) air develops over Canada. This air mass is known as continental polar (cP). The cP air mass will move down towards the United States. As the air mass travels over the Great Lakes, the air is warmed (water has a higher specific heat capacity than land, refer to the article Why is the North Atlantic Still Cold in August?), and the relative humidity increases.

Once the air mass reaches land, the temperature decreases (due to land’s low specific heat capacity), the air cools to its dew point temperature, and precipitation occurs.