Conditions are perfect for the development of the lawn disease known as brown patch. The disease needs warm humid conditions like we're experiencing now. From a distance the lawn looks as if it is suffering from a lack of water, but this is not the case. More times than not homeowners will see the lawn browning out and start watering and watering and water some more. This is a bad idea!! The moisture increases the humidity and makes conditions even more favorable for the development of the disease. Usually, if the lawn is allowed to dry out and weather conditions improve, brown patch won't kill the grass. It kills the leaf blade and after a couple of weeks it will grow out of it. However, if the weather conditions persist and we don't get a cool down it can infect the crown of the grass plant and kill it. As of today, the 10 day forecast looks favorable for brown patch and it is possible that we could see significant damage from brown patch.
How do you tell if it's brown patch and not just a lack of water? If you're watering a couple of times a week and you're lawn is turning brown, it is very likely it is brown patch. Look closely at the leaf blades. If you see brown spots on the leaf blade bordered by a dark brown or purplish margin, that is brown patch.
What can you do to lessen the severity or to prevent it in the first place? First, make sure you're mowing at the highest or second to highest setting on your mower. Make sure to not over water and don't water in the late afternoon or evening. An inch and a half of water, possibly a little more in extremely dry conditions is what your lawn needs to stay green. Also, and most importantly, make sure your lawn dries out between watering's. Try to have a couple of days between watering's to let the soil dry out. An application of Fertilome's F-Stop, a fungicide, will prevent the fungus from developing and reduce the severity if the disease is already present. I would apply it now and every 2-3 weeks through the summer months.