Seed Summer Lettuce
Some varieties of lettuce are more heat tolerant than others, in particular mesclun mixes that grow quickly. Sow more lettuce now for the next wave of cutting. Shade netting will help keep the plants cooler. Or grow lettuce where it's partially shaded by taller crops during the afternoon.
Basil will keep trying to set flowers, yet the flavor is best before it flowers. Pinch plants regularly so they keep producing new, tender leaves. If you make pesto, make several batches throughout the summer instead of waiting until the first frost to pick the entire crop and then stay up half the night making it.
Trim Back Early-Blooming Perennials
Some early summer-flowering, shrubby perennials will produce another flush of blooms later in the summer if you cut them back after flowering. Dianthus, catmint, and salvia all benefit from a trim right after the blooms fade.
Snip Low Tomato Suckers
Tomato suckers, which grow from the axils where the branches meet the main stems, can rob energy from a plant. Yet their foliage makes food for the plant and shields fruits from the hot sun. A compromise between removing all suckers and leaving them alone is to remove the suckers that arise below the lowest flower cluster.
Cultivate After a Heavy Rain
Heavy rains can compact the soil surface, creating a crust that can repel water. Lightly cultivate the surface to loosen it and pull up any weeds before they get a foothold.