I've never planted anything this late, but I'd say it's worth a shot. I've planted beets, letuce, carrots, and mizuna with some success in Mid August. It really depends on the kind of fall we have I think. If it's sunny/mild then you are probably in business. Most of my harvests are smaller than those in summer, but it keeps things interesting in the garden at least. :)

I just planted lettuce in a window box a couple of days ago. We'll see how that works out. My thinking is I can carry it in and out as needed.

I've sometimes had late-planted spinach and lettuce overwinter if there's good snow cover fairly early on--in fact, that's the easiest way for me to get spinach. At this point, varieties that list 30-40 days might be safest--for example, radishes and baby turnips and greens that stand cold and can be eaten at any stage--lettuce, collards, baby kale, etc. I agree, it's worth a shot. If we have a long, warm fall, you could be very pleased with the results!