This is a house in Oklahoma City Oklahoma with extreme water damage to the exterior siding.

This is a perfect example of what could happen when seasonal maintenance isn't performed on a houses guttering system.  During a rain, the water enters the guttering system.  If the gutters and downspouts are clogged with debris, there is nowhere for the water to go but up and over.  Unfortunately, here we see the water ran into the siding causing lots of damage over time.  This potentially very expensive damage could have been prevented with a simple gutter cleaning every season.