Thank you for your question for Extension. Your brown patches could be caused by several things. Not knowing how you fertilize or mow your yard, it could be white grubs which is a common problem with lawns. Here is more information about white grubs:

White grub control in lawns | UMN Extension

Extension has a good publication about taking care of lawns:

Allow some browning in lawns to conserve water | UMN Extension

Without a picture, it's difficult to exactly diagnose your lawn problem. You can send pictures if you'd like another option. If you or anyone living close to you sprayed herbicide or pest control chemicals, this can also affect your lawn.



Thank you for the pictures. Look closely at your grass in the yellowed area and see if it's crabgrass. This is a common weed that takes over an area in a lawn which might be growing sparse and tends to fill in an area. It could be growing in an area where you mentioned there were dog walkers that used that area. Here is information about crabgrass, including how to identify and treat it:

Crabgrass | UMN Extension

It could also be quackgrass which looks different than crabgrass. I think it's more likely crabgrass:

Quackgrass | UMN Extension

Thank you for the clarification of your lawn appearance. I'm sure you have lawn rust, a fungal disease that is common at this time of the year with our warm humid days. I would not recommend fertilizing now in the heat of the summer. It is best to wait until fall. You do not need to apply fungicide either, as rust usually takes care of itself through diligent lawn care. This University of Illinois information is very helpful:

Preventing Rust Diseases on Home Lawns | Lawns | Illinois Extension | UIUC

Here is an Extension page about our rainfall and the growth of rust and other lawn diseases:

What does above-average rainfall and temperature mean for our lawns? | UMN Extension

Good luck in the care of your lawn and enjoy the rest of summer.