For years I struggled with my little vegetable garden. Every year I had renewed hopes for bountiful harvests of tomatoes, beans, squash and other summer vegetables. Then inevitably my beautiful plants developed holes, fried edges, rusty streaks, and black spots. I watched sadly as my hopes withered under blistering summer sun and stifling humidity. I gathered my harvests and was ashamed to admit how paltry they were, despite loving care and too much money. (I once read an article titled, "My Fifty Dollar Tomato." I can identify.)
Then a most amazing thing happened: I discovered cool season vegetables! Why, oh why, doesn't everyone grow these?!
This wonderful cool season vegetable garden is located at Myers Plants and Pottery in Pelham, Alabama.
In my part of the world, winter temperatures drop below freezing but are unlikely to stay there long. Several days last week temperatures plunged into the low 20s. Today, people dressed in tee shirts and shorts were outside jogging and walking their dogs. This schizophrenic weather is typical of an Alabama winter. It can be hard on plants, which too often put out young buds just in time to get zapped by frost. But it also enables year-round gardening.
A host of hardy and semi-hardy vegetables do quite well in my climate. Most of them can endure short periods of frost, and some even taste sweeter for it. The best part is that bugs and disease rarely bother plants this time of year, and I don't have to put on 70+ sunscreen to check on them. (However, I do use a milder sunscreen, always, year round.)
This is far from a complete list, but here are some cool season vegetables to consider:
Hardy vegetables will endure temps down into the low 20s or high teens. They require 3 to 6 hours of direct sun daily. Many will go to seed or develop a bitter taste with rising temperatures. In warm areas like mine they can be planted from late summer to early fall for harvests in late fall, winter and early spring. In regions where winter routinely brings temps into the teens or below, plant these vegetables as soon as the ground can be worked in spring to enjoy a harvest before higher summer temps arrive:
Broccoli 
This was my broccoli last week after a winter storm left a layer of ice over many areas of the garden. Because these were so close to harvest, I did cover them overnight when the temps were the coldest. No harm done! Cabbage
Collards
I did not cover my collards, and they were crusted with ice after a wintry night of ice and snow. They seemed to enjoy the frigid bath.
Kale
My ornamental kale also came through the icy night just fine. You can eat ornamental kale, though I grow it to add color to the winter garden. I grow a less decorative type to eat, though it's deep bluish-green leaves are also beautiful in my eyes. It too had no problems with the ice.
Mustard greens
English peas
Spinach
Turnips
Onions
Semi-hardy vegetables can take temperatures at or slightly below freezing, 29-32 degrees Fahrenheit. They require about 6 hours of direct sun daily. In warm regions, plant in late summer or in late winter. In colder parts of the country, plant in early spring as soon as the ground can be worked, about 3-5 weeks before the frost date:
Carrots
Cauliflower
Celery
Swiss Chard
Before the frigid temperatures, my Swiss Chard 'Bright Lights' was gorgeous. I covered it up, and the hard frost did not kill it. But most of the leaves were wilted. Low 20's was too cold for its comfort!
Lettuce
Potatoes
You can protect your cool season vegetables with a 2 inch layer of organic mulch such as straw or pine bark. Pull the mulch away from the plants in spring.