Spring (April-May) and Autumn (September - October) are considered as the best time to visit Turkey. However, Turkey is considered as a year round destination and the best time to visit depends on the places you wish to visit and the activities you want to indulge in. April and May is the best time for outdoor activities like trekking and cycling or exploring the archealogical sites. June through September are typically hot and dry with temperatures being particularly high making it great for island hoppers and beach lovers.
April, May, September and October are the months with pleasant temperature are considered as the best time to explore the numerous ancient sites of Turkey. From late October, the weather starts to cool off a bit. From November to March, the weather starts to get cold predominantly in interior areas of Cappadocia where the temperature drops to below 0°C. Winters can, however, be the best time to traverse the sites as they are less busy at this time of the year.