August can be a very different month for gardeners depending on their location and the length of the growing season. In the Southern Plains/Zone 7, its planting time for the second cool season/frost tolerant garden, even though it's hotter than the surface of the sun for much of the month.
Adjust irrigation - I water with drip irrigation on timer. At the beginning of the month it will be set to water daily. As soon as I think it's safe to cut back to every-other-day watering, I do. That doesn't always happen in August. It often doesn't happen until some point in the two weeks after Labor Day, but I start being attentive to it in August.
Start seeds - I use the OSU Fall Gardening fact sheet as a guide for when to start frost tolerant plants. I'll direct sow as much as possible but I will start some things indoors so the plants are ready to go in the ground at the recommended time. Soil temperatures, lack of rainfall and air temperatures into the triple digits mean I will start things indoors, but move them quickly outdoors after their first true leaves appear, remembering to harden them off, of course.
Plan for garlic - I've been growing garlic for four seasons and so far I haven't grown it in the same spot once. That's been unintentional but good for crop rotation I suppose. In Zone 7, garlic needs to grow through our winters and needs exposure to cold in order to bulb out in the spring. It isn't harvested until June when the summer garden should already be planted, so I interplant it or find a spot where it can be disguised as an ornamental in a flowerbed. This means I need to have my coming year's garden roughed out in my head to avoid using space I'll need next spring for something else.
Pick the projects - Heavy labor/landscaping work stops in my yard sometime in June when the summer heat sets in and doesn't resume until after Labor Day. Projects to winterize the garden will be done first, followed by finishing up any lingering spring projects. I won't start the work in August, but this month I make notes on what needs to be done so I can determine what order things will be tackled.
Compost - The season will be winding down on many plants. Some, like okra, I'll leave through winter for beneficial insects like native bees. Many other plants I consider safe to compost but some give me pause because I worry about overwintering insects, eggs or disease. If they fall in the safe category, I'll compost them. Everything that won't remain as a food or shelter source for insects and birds through the winter will go to the curb. Going to the curb is always the last resort.
Solarize - I selectively solarize, mostly to treat nutsedge. I say selectively because I have a Bermuda grass lawn and this has also been an especially bad year for crabgrass. Both of these grasses send out runners that I find are easier to remove when they're green. Once they go dormant or are solarized, they break easily which makes it harder to follow them along their runners. Solarizing is good though in areas of weeds that are safe to be turned into the soil.