As you can see from the enclosed photo, the older common Kentucky bluegrass lawns are going to seed right now. When this happens, the plant is using all of its energy for seed head formation and not chlorophyll production, leading to yellow grass.
Along with this annual seed head production, we have experienced less than normal bright sunshine over the last ten days. UV light makes plants green, so we are fighting Mother Nature on both fronts. This annual seeding process will last only a few more weeks and the first day of summer is only 45 days away.
Bright sunshine and long, warm days will be here before you know it.