The weather is this area has been abnormal to say the least. We have had hot and humid days since the beginning of May. With that said, hydrangeas turn brown when there are numerous and consecutive days of very hot weather such as we have had. With the limelight hydrangea flowers won’t brown out as long as they are well watered through hot weather. All hydrangeas turn brown if they wilt too many times in hot weather. Water these shrubs deeply every few days in the heat of the summer (note that hand watering isn’t deep enough) and mulch around plants to hold moisture in the soil longer.