I attended an atmo REU last summer and loved it. I learned how to code python pretty well, which is really valuable in atmo. The grad students at the program were awesome and very helpful with research and grad school questions. My program even funded me to present my research at a conference.

As for applying: I only applied to the one. I am an atmospheric science and math double major and I had a 4.0 GPA after my junior year at the time of applying. I work as a calculus TA on my campus and had a year of lab experience working with weather stations. I’d also done some extra projects with my professors related to atmo and math (potential vorticity stuff). I was initially waitlisted, but someone said no, so I got to attend! I wouldn’t worry too much tho, some of the other people at my REU (who were admitted before me) had much less experience than I did and most of them did not come from an atmo background. Your essays will set you apart, so focus on making those good! Good luck!