There are many different types of clouds, literally dozens if you wanted to get really specific. But basically, almost all clouds fall into one of two categories that can be loosely called "winter clouds" and "summer clouds."

In winter, cold air controls our area most of the time. When warmer air tries to move in, the relatively heavy colder air usually doesn't move easily, so the warm air rises up and over the colder air forming an extensive sheet of layered clouds that meteorologists call "stratiform." These low claustrophobic "winter" clouds often cover many states, and usually bring an extended period of rain or snow.

In contrast, a different mechanism for making clouds dominates during the warm months. Because warmer air tends to be lighter, blobs of the warmest air rise, creating bubbly clouds that we call "cumuliform" - these "summer" clouds build higher into the atmosphere than stratiform clouds, but they aren't nearly as widespread in area.

While these are general rules, it's important to understand that stratiform clouds don't form just in the cold months, and cumuliform clouds aren't solely unique to the warm season. Nonetheless, there is a big difference between the types of clouds that dominate in summer and the ones that prevail in winter.