As TBrom said, first week of August is a little early for clover and cereal grains. Typically in our area, brassicas (turnips, rape, etc) are planted in early August....with clover and cereal grains going in the ground around Labor Day (although last year with the rain and football season, we did not get ours in until Sept. 20th or so....and with the rain we still had great growth).
Spring planting is a tough battle with the weeds. The nice thing about fall planting is the weeds are much easier to control...there might be a few pop up, but the first good frost will zap them. You can seed cereal grains (oats, rye, wheat, barley) pretty heavy (100-150lbs or more per acre) so it does not leave much room for weeds. If doing brassicas in August, the weeds have more of a chance to get a grip. Seeding for those is touchy - not enough seed, you leave space for weeds and your plants do not quickly shade out the weed competition.....too much seed, weeds are not as much of an issue, but the plants compete with each other and yields can suffer.
Rye is a great soil builder as well as weed suppressant - and it grows pretty much anywhere. If you go with rye, be prepared for the tremendous amount of biomass the following spring. If you have the equipment to do so, it is a fabulous choice....but it can get 4-5ft tall, which is makes it difficult to manage without the right equipment.