Maintain a thick layer of mulch around plants to hold in moisture and suppress weeds.
Warm season vegetable seedlings (tomatoes, squash, peppers, eggplant) and seeds (corn, beans) can still be put into the ground through July for fall harvest.
Plant Brassica family seeds (cabbage, broccoli, cauliflower) in August for winter harvest.
Carrots, beets, and turnips can be planted by seed all summer.
(Thank you to California Gardening Magazine, published by the San Diego Floral Association for wonderful seasonal gardening information.)
For a more detailed planting guide, go to Master Gardener planting guide.