Good Morning Dan, 

Thank you for contacting the U of M Extension Service. 

Please click on the following link from the U of M Extension Yard and Garden website: 

https://extension.umn.edu/lawn-care/mushrooms-lawns

These appear to be fairy rings. This information states they appear in cool, wet weather. That is what we've been having in the metro area. 

Here is another link to the lawn care calendar: https://extension.umn.edu/planting-and-growing-guides/lawn-care-calendar

Good Luck!

Good Afternoon Dan, 

If you read through the information I last sent you it states: 

Fairy rings

Sometimes fairy rings develop in lawns especially in the spring during wet, cool weather.

• Fairy rings are arcs or circles of mushrooms growing in dark green, lush grass.
• They are usually 2 to 15 feet in diameter.
• As the fungi break down organic matter, the nutrients cause the grass to grow thicker and darker, and the surrounding lawn develops colonies of mushrooms.

It is caused by fungi, whether the mushrooms actually show up or not. 

It also states: 

• Reduce or turn off your irrigation to dry out your lawn.
• Aerate your soil in the fall to reduce soil compaction and improve drainage.

This area appears to be near the roadway. Is there a possibility of road salt residue affecting your turf grass?  When the weather dries out after all this rain, I believe the spots will disappear. 

Dan, 

You are welcome. Your turf grass looks great to me!