Overflowing gutters rarely announce themselves while it's raining — you're inside, and the sheet of water going over the edge is invisible from the couch. But overflow writes a report at ground level, and you can read the whole thing on a dry Saturday without touching a ladder.
The drip-line trench
Walk the beds under your roofline and look for a clean-cut channel in the mulch or soil, running parallel to the house. That's the drip line — the signature of water going over the gutter's front edge (or off a bare roof edge) and landing in the same narrow strip, storm after storm. Fresh trench edges mean it's active.
Mulch on the sidewalk
Overflow hits beds with enough volume to float mulch and push it onto walkways and the lawn's low corner. If you keep raking mulch back after storms, you're not fighting wind — you're fighting roof water.
The splash line on the siding
Water hitting bare dirt at speed throws a gray-brown spatter a foot or two up the wall. A dirty band along the base of the siding, heaviest under the biggest roof planes, maps exactly where the overflow lands.
The fence mildew line
The black-green stripe along the bottom of fence panels near the house — the one HOA letters mention — is persistent moisture from splash and overspray feeding mildew. The fence nearest the worst gutter run always shows it first.
Drips after the rain stops
Corners or end caps still dripping an hour after the rain quit mean water is standing in the run and working out through a seam — which is a slope and sealant story, not just a cleaning story.
Any two of these signs together mean the system needs attention — sometimes just a cleaning, sometimes slope or sizing. Reading which is which takes about half an hour at your place, and that visit is free.