For reference, here is a list from Wikipedia:
Although in the United States most produce is available year-round, produce is at its best and cheapest in the season it is harvested. Seasonality of produce depends on the region. Below is a general list of seasonality for United States produce.
Spring fruits are apricots, pineapple, strawberries, and mango. Spring vegetables for spring are peas (sugar snap and snow) and more delicate cabbages including mustard greens, baby lettuce, baby spinach and watercress. Also in season are artichoke, asparagus, avocado, new potatoes, rhubarb.
Summer fruits include some berries (blackberries, blueberries, raspberries) and stone fruit (nectarines, peaches, and plums) as well as melons. Summer vegetables include beets, corn, cucumber, eggplant, green beans, tomatoes, zucchini.
Autumn fruits includes apples, grapes, figs, pears, and pomegranates. Autumn vegetables include many cultivars of wild cabbage (broccoli, Brussels sprouts, cauliflower, collards, endives, and kale). Root vegetables (garlic, ginger, parsnips, turnips and yams) and winter squash (acorn squash, butternut squash and pumpkins) are also in season. Corn is in season and peas, seasonal in spring, are also seasonal in late autumn.
Winter fruits include citrus (clementines, grapefruit, oranges, and lemons) and pomegranates. Winter vegetables include hardier cabbages (kale, leeks, raddicchio, and Brussels sprout). Also seasonal in winter are some root vegetables (rutabaga, turnips, and radishes) as well as winter squash.
Some produce, such as onions, lettuce and spinach, are seasonal year-round.