There are many climatic zones in North America, whose climates can be found elsewhere around the world. The climates themselves affect the viability of life, human or otherwise. There are two sets of climatic zones, the ones east of the Rocky Mountains and the ones west. The ones east of the mountains are primarily influenced by warm air masses pushing north from the Caribbean, and cold air masses pushing south from the Arctic. These climatic zones are primarily differentiated by temperature, warmer to the south and colder to the north. The ones west of the mountains are primarily influenced by moist Pacific air coming on shore, and what happens to the air as it passes over the coastal mountain ranges to the Rockies. These climatic zones are primarily differentiated by the amount of moisture in terms of precipitation. Within each climatic zone, there are also internal differences, primarily influenced by elevation.