Fortunately, as fresh ginger root has great health benefits and should be part of your regular diet, fresh ginger is available year round. The quality of fresh ginger root can be a bit variable, however, and it won't last forever as it usually begins to get mold of fungus after a week or so of sitting. You'll want to buy enough for at most 2 weeks at a time, or more if you live in a hot and humid climate where it will go off more quickly.
When you are selecting fresh ginger root to buy, sometimes it can be hard to tell which root will be of the best quality. Sometimes narrow fresh ginger root is extremely stringy and fibrous, and the bigger ginger roots are better. You might think the bigger ginger roots would be the worst, but the bigger roots aren't always the worst quality. If you can find roots with fresh buds and very thin skins, then it is likely they will be less fibrous and stringy - at least in the buds themselves.