Something odd happening this year.
My small back lawn is now a decent mix of grass and clover, which is what I was aiming for. I do not fertilize but tend to toss about compost and corn gluten meal.
Things seem healthy and the weeds are kept at bay.

However, this spring I had someone come by with an aerator to give it a once-over. We have had a great deal of rain so far and you'd think everything would be dandy.

However, after just a week or two of less rain, my soil seems rock hard. The grass is thinning in places where previously it was nice and thick. There is not a lot of walking traffic on there but in spots it looks just like it does.

The only difference I can think of is the aeration. Is it even possible that that wasn't the right thing to do?

I am not a big fan of aeration, but I've never heard of it being a serious issue. Do you have spots that got more or less aeration? Or none? Did he give it a once-over or did he go over it eight times in all directions?

Is the yard shaded?

Could you have nocturnal animals forming a path over the lawn?

I'm asking the questions so I don't offer up a solution and you come back and say, "that can't be because..."

Yes, the soil appears harder than it has been in past seasons, and the grass is thinner (I can actually see the soil in some places now).
Walking on it barefooted is uncomfortable now. Perhaps I'm walking on the aeration plugs that didn't dissolve? But this was done two months ago!

The area was done evenly, but he only went over it once. Eight times??? That would have turned the sod into a muddy mess!

There is no change in light conditions. The lawn is a bit challenged by a very tall nearby arbor vitae which sucks up a lot of moisture but that was the case last year, too. The dry spots nearer the hedge are explainable. I had the top three feet taken off that hedge last year.

The grass gets partially gets some shade from the hedge in the morning and a nearby maple in the afternoon, but only for a few hours.

The only nocturnal animals here are cats and occasional raccoon. (the raccoons being the less annoying of the two)
I've been careful not to walk on the thinner spots while gardening.

The situation this year seems ideal. What about last year? Did you have normal precipitation? Do you otherwise irrigate the lawn? If so, how long and how often?