While most people enjoy sitting in a baseball stadium on a clear day, the bright sunlight can blind players, leaving them unable to see a hit baseball. The bright blue sky can also make it hard to determine how high the ball is in the sky. Most baseball stadiums are set up, so the right fielder is the only player that is looking into the sun.
However, cloudy skies can also impact the visibility of the ball in the sky. Sometimes the baseball can blend in with clouds, making it hard for an outfield to distinguish it with the clouds as a backdrop.