Turkey is a year-round destination depending on your itinerary. Although the tourist "high season" (with associated higher rates)is from mid-June through mid-September, Spring and Fall are the best seasons to travel. The sun is warm and skies are generally clear. You can expect mild to very warm temperatures and little rain during this time. Summer temperatures on land can be hot and humid, but cruising along the coast is always pleasant.
Turkey is a large country with wide climatic variations according to its distinctive regions. Humidity is moderate (40%) along the Aegean coast and somewhat higher (50%-60%) in Istanbul, and along the Black Sea. The coastal region is fairly warm throughout the year with average temperatures ranging in the 70ºs-80ºs F in spring and summer. On the Anatolian plateau daytime temperatures can be quite hot (90ºs in July) with cool evenings requiring a medium weight jacket or sweater. By late October there is a chance of light snowfall.
Trekking season in the Kackar Mountains is short, between June and late August. Mountain weather conditions fluctuate and you may experience some rain near the Black Sea. Daytime summer temperatures in the mountains can rise into the 70ºs F, falling to the low 40ºs F at night.