The climate, classified as Mediterranean, has a wet, windy, and cool fall, winter and spring, and a drier, warmer summer. The average annual precipitation is about 33 inches. The majority of this falls as rain, although there is some snow in the winter. The average temperatures are very similar to those of North Georgia, except the cold period lasts longer and begins much earlier.
The prevailing winds are from the northeast and east in the summer and from the south in the winter. These winds can be quite strong at times, and the hillside position guarantees breeze circulation most of the year. Early morning valley fogs occur frequently in the fall and winter and taper off somewhat in the summertime.
Physiography (The Shape of the Land)
The comune can be divided into three areas. There is a mountainous woodland/ pasture area above 500 meters (the Mountains of Cortona) which extends across the northern and northeastern section, covering approximately 17% of the comune. The second area is called slopeland and lies between 300 and 500 meters in elevation covering approximately 40% of the comune. This area includes the Chiuso Hills in the eastern part, as well as the mountainous foothills in the north-eastern part. The third area consists of lowlands, which lie below 300 meters in elevation. This includes roughly 43% of the comune. The town of Cortona is located at 651 meters in elevation at the Santa Margherita Church and 500 meters at Piazza Garibaldi.
Mountainous Area: The bedrock (underlying rock structure) consists of interbedded strata (or layers) of shale, limestone, and sandstone, all sedimentary in origin.
Slopeland: This consists of interbedded sedimentary strata with sandstone prevailing. In the Chiuso Hills, sandstone is predominant.
Lowlands: The lowland areas consist of underlying sandstone and shales with layers of sand and alluvium (material deposited by streams from the surrounding slopes) on top.
In brief, the geology indicates that the area was largely marine in origin, dating back 30-40 million years. The lowland areas around Lake Trasimeno suggest that this lake was much larger than it is now, probably at its largest in Pleistocene times, between 2 and 5 million years ago.
There is a mixed broadleaf, evergreen, and deciduous shrub forest in the mountainous region. This vegetation is continuous or discontinuous depending on the slope and orientation of the area. Some of the deciduous trees found are poplars, elms, chestnuts, oaks, and beeches. The evergreen trees include spruces, cypresses, pines, and olives. The most common vegetation association found in the rest of the comune is that of the "maquis" or low shrub vegetation. This includes brooms, heathers, heaths, and junipers, etc.