You can't really hurt the grass...its brown already. Not optimum conditions, but I would go ahead...assuming it will rain in a few days. Then as the weeds attempt to grow, they will be killed. And the fertilizer would begin to be absorbed by the grass...you did plan to fertilize didn't you? With luck the grass will begin to recover. Give it some help.
Has anyone noticed? The long summer dormancy has caused some plants and weeds to come out of dormancy as if there had been a winter instead of a hot summer. Dandelions are blooming in some areas here, also oxalis.