Gwinnett is located in North Georgia just south of the Blue Ridge Mountains and enjoys a favorable climate. The mountains form a partial barrier to cold air masses moving eastward across the US, and as a result, there are few days in the heart of winter when the temperature falls below 32° Fahrenheit. Average highs in the summer are in the high 80s with lows in the uppers 60s, while average highs in the winter dip to the 50s and lows in the upper 30s. Even in the hottest weather, early morning temperatures usually drop into the lower 70s.

There are typically about 220 days with sunshine each year. Rainfall is well distributed throughout the year with July and August having the greatest amount of rainfall and October and November the least. There are times in spring and summer when soil moisture is low. This usually results from long periods between rains rather than from a shortage of total rainfall. Most summer rain is produced by thunderstorms, which can be accompanied by strong winds and intense rainfall.

Gwinnett is far enough from the coast that effects from severe coastal storms are reduced. While snow and sleet usually occur each year, substantial accumulations are rare.