When you mean "starting with one thing then ending with something different", the word is countable. When you mean "leftover money after paying for something", it's uncountable.

Hi: I agree with Peachy, although I think he accidentally switched "countable" and "uncountable." You count the change from a monetary transaction: "I used a dollar for a twenty-nine cent purchase; and my change was two quarters, one dime, two nickels, and a penny: seventy-one cents." With "change" as in "make something different" or "exchange on thing for another," the singular and plural are largely interchangeable to my (native American English-speaking) ear. The exception would be when you want to emphasize that the change is singular: "the only change in the weather was a sudden drop in temperature," or plural: "we need to make quite a few changes around here."

Either sentence about weather is correct depending on what you are trying to say. It is still a question of being plural or singular. If I am thinking only about a single major change like overall weather conditions being different with each season then I would say, "We experience change in the weather with each season." However, if I am thinking of all the various weather changes in a season then I might use "changes." Either can be used comfortably in conversational speech.

No, Gabe's last sentence is more natural. I'm not sure why, but plural sounds best to a native speaker in this case. I suppose because the idea is that we're talking about all of the variables, e.g., temp, precipitation, etc.

Then what about 'we experience change in the weather with each season.'?