This may be true, but most Android devices ship with some kind of weather widget built in (often on the home screen) in a much more visible way than the iOS weather app. You'd think that would mean there would be more demand for the iOS app.
The visibility on iOS might depend on how often normal users access the status tray. I have the weather widget in it, so even when not interested I get to see the forcasts five or six times a day at least.
I wouldn't imagine buying a app for basic weather checking.
The 51/49% split there is interesting.