What is a large body of air that has nearly the same temperature and humidity?

Air mass. A meteorologist would know this term, for it is the context in which air mass is used. Air masses can cover up to hundreds, as well as thousands of miles. No matter what distance they travel, they adapt to the surface that is below them.

Polar and artic are terms for areas with colder air masses. Tropics is the term for areas with warmer air masses. There are also maritime air masses. This one affects locations such as the Gulf of Mexico and Florida. Superior air masses are around as well, and they are dry and don't often reach the ground.