That's not entirely true! Cold air masses can combine with warm air masses, and they do so quite frequently. This interaction is a key driver of weather patterns and is responsible for many weather phenomena. Here's why:

* Fronts: The boundary between a cold air mass and a warm air mass is called a front. There are two main types:

* Cold fronts: When a cold air mass pushes into a warm air mass, it forces the warm air upward, leading to potential thunderstorms and strong winds.

* Warm fronts: When a warm air mass pushes into a cold air mass, it slowly rises over the cooler air, often causing widespread, gentle rain.

* Weather Systems: The interaction of these air masses is the basis for many weather systems, such as:

* Mid-latitude cyclones: These storms involve the interaction of cold and warm air masses, leading to rotating winds and precipitation.

* Thunderstorms: Powerful updrafts generated by the rising warm air in a cold front can lead to thunderstorms.

So, what happens when they combine?

They don't simply "combine" in the sense of blending into one. Instead, they interact in complex ways, leading to changes in air pressure, temperature, and moisture content, ultimately causing a variety of weather phenomena.

Let me know if you'd like to delve deeper into any of these concepts!