To me, summer is dirty feet.
I absolutely cannot keep my feet clean in the summer. I am one of those people who loves to walk barefoot. I always have. And, thus, I have always had dirty, filthy feet all summer.
When I was a kid, I would be all over the neighborhood sans shoes. My mother made me wash them before dinner - though I don't know why, we didn't eat with our feet in my house - and inevitably I would get in trouble again for leaving nearly black washcloths in the bathroom. Still not sure what she was on about there, I was doing what she asked.
Today I tend to get the ring-around-the-heel, and no amount of washcloth application will get it out because that dirt is delicately ground into my skin now. I need to soak and scrub my feet clean a couple times a week. I only go barefoot around the house, not outside anymore (rocks, chicken poo, pine needles, etc.), but that is plenty good enough to get my feet dirty.
I have a particular pair of pink flip flops I wear when I walk the dog. They have soft, spongy, foamy soles that keep wet once they've gotten wet, and often that helps keep my feet fairly clean. It's usually not enough, though, and I still have to go at them with the pedicure cheese grater thingie.
I was looking at my feet at work the other day, cleverly disguised in nice sandals, and I saw that light ring - I can get away with one more day without scrubbing, but not two - and that's when I realized that this is what defines summer to me. Not home grown tomatoes, not swimming pools, not fireworks.
Just dirty feet.