Rodents. You're not likely to miss an animal in the gutter at night, especially when it's a rodent because of the noise they create. Squirrels, chipmunks, rats, mice, and other rodents may discover your drainage system as a welcome refuge once temperatures ease.

Dirt, dried leaves, twigs and other debris often make their way into your gutters due to wind and rain. Wind can bring small organic materials from your yard and neighboring houses into your gutters. The rain can also cause the dirt on your roof to travel into your gutter system.

Insects like mosquitoes, wasps, millipedes, and centipedes, among other creepy crawlers, are often found inside open-top gutter systems that aren't cleaned and maintained properly. Because debris like leaves, dirt, and rocks can get trapped in an open-top gutter system, clogs occur.