I am a very diligent mower, I 'comb' the lawn twice-annually with a push tining tool, and I scout the lawn every day for anything out of the ordinary.

How often do you water and for how long?
How high/low do you mow?
How often do you fertilizer and with what?

If the centers of the circles are the trees, it's likely that the trees are using too much water. Some maples are notorious for having shallow roots, and may be using enough water that the grass can't thrive when there's not enough rain.

If the circles are just near the trees, a fungus is more likely, although I would expect it to manifest in wetter weather rather than dry weather.

BTW: the circles under the maples are nothing more than the grass competing with them for moisture during drought conditions or extreme heat --- the grass turns emerald green once there's enough rain and the temps moderate.

Again my apologies for not being clear.

Still you have the occasional weed and patches of clover. Some people find that ghastly.

Okay, so you do have a question. Scott's is selling fertilizer all year long so they can pay for their executive's boats and second homes. Now you are here and getting the benefit of all of our collective experience reading these forums for 10 years. During those years hundreds of people have come and gone but a few of us are still here. Hopefully we remember what we've read and learned.

The experience with fertilizers is that 2/3 to 3/4 of all your annual nitrogen should be applied in the fall. The rest should be applied in late spring after the spring flush of growth has abated. That is not the Scott's agenda. If you are using Scott's products, fine - just understand that the timing is a consideration for the health of your grass. Applying the spring fert after the flush of growth (Memorial Day) will carry your lawn until late summer (Labor Day). Then an app on Labor Day will carry you to Thanksgiving (third and final app). I use these days because they are easy to remember. They are not cast in concrete at all. Do what comes natural to you, but do not apply later than Memorial Day for fear of burning the grass. Applying in early spring will amplify the spring flush so that you have to mow 3x per week to keep it from covering your house. So those are your parameters and the reasons for the schedule.

If you are watering in addition to rainfall, the general consensus is to water once a week in the heat of summer. Water long enough so the grass will survive a full week. Getting to that point can sometimes be a project in itself. In my case we are having an extraordinarily hot (temps near 100), dry (4 inches of rain since October), and arid (very low humidity) summer. Normally I would water once a week for 3-4 hours per zone. This summer I am going to a 7-hour schedule starting tomorrow. Your mileage will vary due to the above factors plus shade, sun, clouds, wind, soil type, grass type, grass mowing height, and your sprinkler's ability to provide water.

I have to give kudos to dchall for planting the seed in my head and cultivating the organic approach to lawn care here on this site. It certainly has worked for me.