When temperatures are high and there has been excess moisture fungi can breed in your soil and cause problems in your turf.  Most of the time fungus problems will correct themselves.  If you are noticing changes in your grass color or dead/dying spots and it is getting worse, you might need an expert analysis of your lawn.  We can tell you what you are doing wrong causing fungi to live and breed in your turf and offer a diagnosis and treatment.  In some cases fungicides need to be applied to correct conditions.