Answer: I don't know if the Weed and Feed had an adverse reaction (maybe from over-application), or if your lawn was so full of annual grasses that the weed and feed killed them. Some grasses are considered cool season grasses (fescue is a good example) and will thrive when temperatures are cool but will die back when things get hot. Other grasses (Kentucky Blue and Bermuda) are warm season grasses. They will remain green during the heat of the summer, but will die out when temperatures get cool. To have a really green lawn most of the year, you may want a combination of warm and cool season grasses as your turf. In any case, I'd rake out the dead grasses and weeds, then reseed with perennial rye. It should green up in a week or two. Turfgrass should be deeply watered once or twice a week (depending upon weather) to promote a deep root system. This will help it endure the hot summer temperatures without needing a daily watering.
Best wishes with your lawn.
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