The usual reasons for changing traffic and runways are weather and maintenance related. Wind direction, runway visibility, and other factors dictate the safest departure and approach routes.
I live in the Chicagoland area, with one major airport on the north side of Chicago (O’Hare), and a smaller but nonetheless busy airport (Midway) on the south side of the city. I live in the western suburbs of Chicago. Upon occasion, the traffic heading for O’Hare Airport goes over my Village. It’s arbitrary. I was once told it is because they rotate the flight patterns so as to share the wealth, so to speak, of the air traffic noise amongst all of the Chicagoland area rather than just the same route over certain towns all the time. Spreading the noise misery, as it were.