Rust accumulates on car brakes due to moisture, but brake rust should not alarm you. This is a regular occurrence and continued brake use will quickly eliminate the rust layer.
Reasons
Rain, humidity and car washes all expose your brakes to moisture. If the car sits idle in these wet conditions rust may accumulate on the brakes. However, this does not always occur even if the car sits for a long period of time.
Significance
If rust is on your brakes, it may cause a a screeching sound for a few stops. However, this sound quickly dissipates because the brake pads naturally wear the rust off the brake rotors. Brake rust does not affect brake function or driving ability.
Solutions
If all the rust does not disappear naturally, you can use brake cleaner and a wire bristle brush to clean it off. Using water repellent paint to cover your brake rotors and rims may help to minimize rust accumulation in the future. But do not paint the rotors themselves.
