Northern & Central Midwest
Water Under the Mulch
Make sure water is getting under your mulch. If things dry out too much and you need to water, check carefully after watering to make sure the mulch didn't shed water. If necessary, pull back the mulch and spot water shallow-rooted plants like peppers and eggplants.
It's hot, but keep after weeds. If they catch hold, they will sap the water and nutrients from your vegetables. Right after you finish watering or it rains, get out that hoe and slice them off just below soil level. If you keep doing this, even perennial weeds will eventually give up.
Let Lettuce Re-Seed
Lettuce, endive and other summer greens should be finished and left to go to seed. They aren't beautiful, but if left to seed, will plant your fall crop for you, not to mention next spring's crop. Once seeds are set you can also cut off the seed heads and simply lay them on the soil.
Harvest Cherry Tomatoes
Harvest cherry tomatoes regularly. Expect them to crack after a rain, so if rain is coming, it helps to harvest them beforehand. They will continue to ripen on the counter in the kitchen. If they crack you can simply drop them to produce plants for next year.
Dig garlic when three-fifths of the leaves turn brown. Gently lift with a garden fork and leave to dry in an airy spot for two or three days (protect from rain). Then bring in out of the sun and dry for several weeks before moving into a cool basement or braiding and hanging in a dark, dry spot.