I am always amused when friends from the northeast tell me how wonderful it must be to garden in a "mild" climate. "Mild" is not the first word that comes to mind when I think of the climate here.
Officially, Cary is located in USDA Hardiness Zone 7B, where the average low temperature in the winter is 5 - 10°F. The weather service tells us that there are 60 - 90 days per year in which the temperature exceeds 86°F. It also informs us that yearly rainfall averages approximately 46 inches.
Unofficially, it hardly ever gets down to 5 or even 10 degrees in the winter. Coming from New York, I find Cary winters to be a piece of cake - blue skies, hardly any snow, and I can take off my down coat by 11:00 in the morning. For plants, though, it's kind of betwixt and between. It's cold enough to kill your tropical hibiscus, but not cold enough for your tulips to come back. As for the warm season, you are probably safer assuming 90 days of 90 plus weather. That should cover the summer (which you would expect to be unremittingly hot and humid) as well as the occasional 90 degree spell in April or October. The official tally of 46 inches of rainfall is deceptive also, since the rain likes to come in the form of torrential downpours that flood the streets and yards, and is often followed by weeks and weeks of dry, hot weather.
One more thing: as anyone who has dug a hole here can tell you, the soil is clay.