August is a good time to start thinking about hearty vegetables that can take all kinds of temperatures. Planting cool weather crops such as spinach and kale are a good option. If you start from seeds you can time it that the seeds will sprout and establish themselves.
August is the time to plant your fall, or cool weather crops. Some ideal things to plant are spinach, kale, lettuce, collard greens, and snow peas. Other crops like broccoli, cauliflower, and cabbage will also grow well.
I recommend vegetables that take a short time to mature and that would be minmally affected by an early frost. Radishes are harvested about a month after seeds are sown. Also, hearty plants such as turnips and rutabagas can be safely planted in August.
This really depends on what region of the country (or the world) you live in. If you live in the southwest, where it's extremely hot in August, succulents are great for this sort of weather. They do not need much water and love the heat.