Here's why:

* Continental: This part of the name refers to the fact that the air mass originates over land.

* Air mass: This term describes a large body of air that has relatively uniform temperature and humidity.

Continental air masses are typically dry because they form over land, which has less moisture than oceans. They can be either warm or cold depending on the temperature of the land where they form.

Here are some examples:

* Continental Polar (cP): Forms over cold landmasses like Canada or Siberia. It's cold and dry.

* Continental Arctic (cA): Forms over even colder landmasses like the Arctic. It's very cold and dry.

* Continental Tropical (cT): Forms over hot landmasses like deserts. It's warm and dry.

Let me know if you'd like more information about specific continental air masses!