Cortona is located in Tuscany, which has a very warm and pleasant climate. The best time of year to visit Cortona is in the spring or summer. If you visit during this time of year, you will get the best weather, as well as the chance to see some of the festivals that take place. A lot of wine in produced in this region of Italy, and you will get a chance to tour some of the vineyards and do wine tasting, which is often best during the warmer months. If you visit in the fall or winter, you will get some colder weather, as well as a lot of rain. The rain turns everything to mud and mush, and it is just not a good time to be around Cortona. If you are going to be visiting in the spring or summer, you should pack shorts and t-shirts, but you should also keep in mind that this will make you stick out as a tourist. Most Italians don't wear shorts or t-shirts, but if you want to be comfortable, that is what you should go with. If you visit in the fall or winter, you should bring pants and heavier tops, like sweatshirts and jackets. It can get quite cold at night, especially in the winter.