Why Continental Climates are Extreme

Heat Capacity of Large Water Bodies Moderates Temperatures

Jul 23, 2008

The heat capacity of water and thermal physics explain why continental locations have more extreme temperatures than coastal locations.

In Kansas and Nebraska, which are near the center of the North American continent, summer temperatures can well exceed 100 degrees F and winter temperatures can plummet to 30 below zero or colder. Coastal areas of North America can be hotter, if they are far enough south, or colder if they are far enough north. There are however no coastal areas with this wide range of temperature extremes.

Continental climates have much more extreme temperatures, both hot and cold, than climates at similar locations near a coast or other large body of water. Why?

Specific Heat and Heat Capacity

Physicists use specific heat and heat capacity to measure the amount of thermal energy that is needed to change the temperature of objects. The heat capacity is a function of both the type and amount of material. Hence Lake Superior will have a larger heat capacity than a small pond because it contains a much larger mass of water. The specific heat is the heat capacity divided by the mass, so it is a property of the type of material but not the amount. Because they are both made of water both Lake Superior and the small pond have the same specific heat. The salt in seawater will affect the specific heat only a small amount.

Water Moderates Temperatures

The specific heat of water is a little over 4000 joules per kilogram per centigrade degree. The specific heat of land varies more depending on the type of rock or soil, but an average value is a little over 1000 joules per kilogram per centigrade degree. That means it takes four times as much thermal energy to raise or lower the temperature of a kilogram of water as a kilogram of land.

In the hot parts of the summer, solar energy warms things up. However near the oceans or large lakes roughly four times as much solar energy is needed to raise the temperature of a kilogram of water as a kilogram of land. (A few minor complicating factors are being ignored here, but they have only a small effect.) Hence it takes much more solar energy to warm coastal areas than to warm inland areas. Kansas, Nebraska, and other continental areas can therefore get much hotter in summer than the Atlantic or Pacific coastal areas of the same latitude.

In the cold parts of the winter, there is less warming solar energy, so it gets cold. To lower their temperatures, bodies of water must release more energy into their environment than land masses need to. Hence coastal areas to not get as cold as inland areas. Continental areas, such as Kansas and Nebraska, are therefore much colder in winter than coastal areas at the same latitude.

For cooler summers and warmer winters, live near a large body of water. Those liking extreme temperatures, both hot and cold, should move inland.