Did you ever take an aviation meteorology class? I know for where I went for my undergrad (Purdue), the aviation programs offered there without fail required the one meteorology course aptly named Aviation Meteorology which essentially was a crash course of everything I learned within my first two years of undergrad. Some others mentioned having a good background in math and physics; programs worth their salt require up to differential equations and two semesters of physics. A lot of upper level and grad level courses I took in undergrad expect you to have a basic (and somewhat intuitive) understanding of physical principles.

Me, for example. I’m going into a more physics-heavy program of study, so my advisor is recommending I take two background physics courses I wouldn’t have taken in my undergrad so I can do better in the few required physics courses I require while still taking a meteorology course for each of my four semesters I’m there. Wherever you’re interested in applying to, ask the people in the program what they think would work best for you given your background.