Map from Google - Turkey

In Turkey there is a noticeable variety of climates, with considerable differences between the areas, and even with some microclimates determined by the exposure of slopes and coasts.
The coastal areas have a generally mild climate, but the coast of the Black Sea is cold than that of the Mediterranean. The inland areas have a continental climate, with cold and snowy winters and hot and dry summers, but usually with cold nights.
Summer is dry and sunny throughout the country, except on the north-east coast. In all inland and south-central regions, the driest months are July, August and September.
The map below shows the climate zones of Turkey.
Climates in Turkey
1- Eastern Thrace

In this area of Turkey, south of Bulgaria, where the city of Edirne (the ancient Adrianople) is located, the climate is slightly continental: winters are quite cold, with a January average of about 37.5 °F, and summers are warm, and tempered by the breezes. In winter, cold spells may occur, with snow and frost, as well as heat waves in summer. The rainfall is not abundant, but it's well distributed throughout the year, with a relative minimum in summer, when, however, brief thunderstorms may occur.
Here are the average temperatures of Edirne.
Average temperatures - Edirne
Min (°F)303236455459636355484134
Max (°F)434855667584888881705746

Rainfall in Edirne is not abundant, but it is well distributed throughout the year, with a relative minimum in summer, when there can still be some brief thunderstorms. Here is the average precipitation.
Average precipitation - Edirne
Prec. (in)2.4221.821.

2- Istanbul and the northern coast

In the area of Istanbul and Bursa, in the small portion of Europe and in the area beyond the Sea of Marmara and the Straits of Bosphorus and Dardanelles, the climate can be described as transitional Mediterranean, with relatively cold winters, and warm and fairly sultry summers. In Istanbul, the January average is around 42 °F, but when air masses coming from Russia move over this area, there may be some cold and rainy days, and even snow (in Istanbul, there are about 15 days per year with snow, mostly from December to March). Summer is the least rainy season, and August is the driest month, while autumn and winter are the rainiest seasons. The average temperatures are around 73.5 °F in July and August.
Average temperatures - Istanbul
Min (°F)373637455461646661554841
Max (°F)464852617077828275685952

The sea in Istanbul, very cold in winter, becomes warm enough for swimming in July and August, as we can see in the following table.
Sea temperature - Istanbul
Sea (°F)484646505968737572665752

In the southern part of this climatic zone, the ruins of ancient Troy are found.
Along the coast east of Istanbul, winter becomes slightly milder, and summer progressively more rainy. For example in Trabzon, the average temperature in January is 45.5 °F, and in July and August it's 74 °F.
Average temperatures - Trabzon
Min (°F)413941485563686863575045
Max (°F)525254596673797975686155

In Trabzon, 32 inches of rain per year fall, with a summer minimum: 1.4 inches in July, 1.8 inches in August. Here is the average precipitation.
Average precipitation - Trabzon
Prec. (in)

In Trabzon the sea is slightly warmer than in Istanbul, and is warm enough for swimming from July to September.
Sea temperature - Trabzon
Sea (°F)504848526170757773686154


3- North-East Coast

The easternmost part of the Turkish coast of the Black Sea, east of Trabzon, from Rize towards the east, has a climate that can be defined almost oceanic: the average temperature is similar to that of Trabzon, but the rains are abundant in all seasons, so that even more than 80 in of rain per year fall, although actually the summer rains are not continuous, but are concentrated in periods of bad weather which last a few days.
Here is the average precipitation in Rize.
Average precipitation - Rize
Prec. (in)

Winter is milder than in the area of Istanbul, with less frequent snowfalls. Here are the average temperatures.
Average temperatures - Rize
Min (°F)393741465563686863554841
Max (°F)525254596675798175686155

4- West Coast

Along the west coast of Turkey, overlooking the Aegean Sea, where the remains of ancient Greek cities like Pergamum and Ephesus are located, the climate is Mediterranean: winter on the coast is mild, with an average in January around 48 °F; cold waves may still occur, but they are shorter and rarer than in the area of Istanbul. In Izmir (Smyrna), there are on average only 3 days with snow per year.
Average temperatures - Izmir
Min (°F)434345525966727264575246
Max (°F)545561707988919184756457

Summer is sunny and hot: the maximum temperatures are around 86 °F along the coast, and increase to 93/95 °F towards the interior, in the western valleys where cities like Pamukkale are found. The peaks of heat are around 105 °F. Summer, however, is tempered by the breeze along the coast of the Aegean Sea, while at times the breeze is replaced by a strong and persistent wind, called Meltem.
At Izmir the sea is never very warm, because in summer the north wind prevents the sea to warm up by much.
Sea temperature - Izmir
Sea (°F)595959616472737372686461

The rainfall amount in the west coast goes between 27.5 and 40 inches per year, with a maximum in winter and a minimum in summer, when it almost never rains.

5 - South Coast

Along the southern coast of Turkey, and in the short stretch of coast north of Syria, the climate is Mediterranean, but warmer than in the west coast, and even more so than the Black Sea coast. Winter temperatures are quite mild, with average highs around 59 °F, while in summer the maximum temperatures are definitely high, ranging between 86 and 95 °F. Rainfall is concentrated from mid-October to mid-April, when it can be abundant, and can sometimes be torrential, particularly in slopes facing west and southwest. In Antalya, about 40 in of rain per year fall, but it almost never rains fromr June to Spetember. Here is the average precipitation.
Average precipitation - Antalya
Prec. (in)

Here, the average in January is 50.5 °F, that of July is even 82.5 °F.
Average temperatures - Antalya
Min (°F)434346525966727266595246
Max (°F)595964707788939388797063

At Antalya the sea is warmer than in the north and west coast, and is warm enough for swimming from June to October.
Sea temperature - Antalya
Sea (°F)636361646875798179757064

6- Anatolian Plateau

In the vast inland plateau, the climate is continental, with significant variations between night and day and also between winter and summer. Rainfall is scarce, around 12/20 inches per year, with a maximum in winter and minimum in summer, which is normally sunny. In this area, the climate is fairly uniform, and varies mainly with altitude, however, it becomes progressively more continental in the east.
The capital of Turkey, Ankara, is located in the center of the plateau, about 3,000 feet above sea level. Here winter is cold and snowy, with a January average of 27.5 °F, but the temperature drops with relative ease to -4 °F, during cold air outbreaks from Russia. Summer is hot and dry, sometimes torrid during the day, when it can reach 100/105 °F in the worst moments, while the nights remain generally cool. Here are the average temperatures.
Average temperatures - Ankara
Min (°F)212330374348545446373027
Max (°F)343950596875818275645039

In Ankara, the annual precipitation is around 14.2 in, therefore it's not abundant. Here is the average precipitation.
Average precipitation - Ankara
Prec. (in)

In this area, at about 3,600 feet above sea level, we find the region of Cappadocia, where lies the city of Goreme, famous for the "fairy chimneys" or "earth pyramids". Here the climate is similar to that of Ankara, the average January temperature is just below freezing, and snow is quite frequent (the landscape of this region have an even more magical look under the snow), while the average in July and August is around 71.5 °F, with highs around 84 °F, but with possible torrid days.

7- Eastern Plateau

In the easternmost provinces, near the border with Georgia, Armenia and Iran, the climate becomes really harsh, not only because of the higher altitude, which generally ranges between 4,000 and 5,200 feet, but also because of the proximity with Russia, from which cold air masses may arrive, so that during winter this is one of the coldest areas not only of Turkey, but of the entire Europe. Lake Van, at 5,200 feet above sea level, is large enough to temper a little the climate, especially in winter, so that the average in January along its banks varies between 25 and 28 °F, but further north, in the provinces of Erzurum and Kars, the January average drops to nearly 50 °F at 5,000 feet.
Average temperatures - Van
Min (°F)181827364552575752433223
Max (°F)363643556475828275635039

The rainfall pattern in this eastern part of the plateau is similar to that of the rest of the plateau where Ankara is located, therefore precipitation is not abundant, with winter snowfalls and dry summers. Here is the average precipitation in Van.
Average precipitation - Van
Prec. (in)1.4122.

In Erzurum, a city of 360,000 inhabitants in the north-east of Turkey, at 5,600 feet above sea level, the average temperature in January is 16.5 °F, so it's colder than a northern Europe city like Helsinki. The cold record is -40 °F, and that of April is still 1.5 °F. Summer is quite warm during the day, but the nights remain cool and sometimes even cold. There are, however, hot days with peaks of 86/91 °F . Rainfall is not abundant, just 17.5 inches per year, with two minima, in summer and winter, and a maximum in spring. During winter, however, there's no shortage of snow, which can sometimes be abundant.
Average temperatures - Erzurum
Min (°F)91019324146525245362714
Max (°F)252736526370798172594530

8 - High Mountains

In Turkey there are several mountainous areas, where the altitude exceeds 6,500 feet. They range from the Olympus of Mysia (Uludag), in the northwest, near Bursa, where you will find the most famous winter sports resorts, to the much higher mountains of the north-east (Pontus), south-west (Taurus), and of the eastern regions, where Mount Ararat stands out with its 16,854 feet. In the map above, we colored the mountainous areas in brown. Here the climate is alpine, and of course the temperature decreases with altitude. At higher altitudes, for instance on Ararat, there are glaciers and permanent snow.

9 - Southern semi-desert areas

In the south-eastern provinces, near the border with Syria and Iraq, from Diyarbakir and Batman towards the south, the altitude ranges between 1,300 and 2,300 feet. Here the winter is quite cold, averaging a few degrees above freezing and with possible snow and frosts, more frequent in the northern part, but the main feature of this area is the hot summer, with temperatures that can exceed 113 °F.
In Diyarbakir, at 2,230 feet above sea level, the average in January is 35.5 °F, while the average in July is 86 °F. The lowest recorded temperature is -6 °F, the highest is no less than 116.5 °F.
Average temperatures - Diyarbakir
Min (°F)283036455261727061503932
Max (°F)45485768819110010091776148

Here too the rainfall is not abundant, and is concentrated in the cold half of the year, while in summer it rains very rarely. Here is the average rainfall.
Average precipitation - Diyarbakir
Prec. (in)

Further south, in Cizre, at 1,300 feet, near the border with Syria, the average maximum in July is no less than 106 °F, while the daily average in January is 43.5 °F, so winter is usually quite mild. Here the rains are a bit more abundant, around 19 inches per year, given the proximity of the mountains, but here also in summer it rains very rarely. Here are the average temperatures.
Average temperatures - Cizre
Min (°F)363945525968737266574639
Max (°F)52556372849710610497826655

when to go

Almost the whole of Turkey, except the north-eastern coast, enjoys a dry and sunny summer, but it can be very hot, even on the coast. So in general it is preferable to visit the country in spring and autumn. The weather is nice already in April along the west coast (see Izmir); in May, June and September in Istanbul; in May, June and September in the Anatolian Plateau and Ankara (with a preference for the month of May, and remembering that nights can be a little cold); in April, May and the first half of October along the southern coast and in the semi-desert areas of the south-east; in June and September in the eastern highlands; in July and August in the high mountains.

For a beach vacation, along the north and north-east coast the best months are July and August, but remember that east of Istanbul, summer is not very sunny, and can be rainy, especially in the areas most exposed to the westerlies (while bays such as that of Samsun are relatively sheltered). In the easternmost part of the coast, it goes even worse and the rain may be abundant even in summer.
Along the west coast, the bathing season runs from June to September, the temperature is high and the sun shines. However, as we have seen, the sea is slightly cooler, and sometimes the Meltem, the northern wind, blows.
Along the southern coast, summer is very hot, so you may prefer the months of June and September, to avoid the period of the most intense heat, which beyond a certain level, you can feel even at the sea.

What to pack

In winter, on the north and west coast (Izmir and Trabzon), and in the south on the border with Syria, warm clothes, sweater, jacket, raincoat or umbrella. In Istanbul, warm clothes, down jacket, scarf and hat for cold spells; in Antalya and the south coast, spring/autumn clothes, sweater, jacket, raincoat or umbrella. In Ankara and the plateau, very warm clothes, down jacket, hat, scarf, gloves.
In summer: on the west and south coast (Izmir, Antalya), light clothes, light sweatshirt for the evening, scarf for the breeze; on the north coast (Istanbul, Trabzon), you can bring a sweatshirt or sweater for safety; in the eastern part of the Black Sea coast, a raincoat or umbrella. In Ankara and the plateau, light clothes for the day, sun hat, a sweatshirt or sweater for the evening; in the eastern part of the plateau, you can add a jacket for the evening. In the south, on the border with Syria, lightweight clothing, of natural fibers, desert turban, possibly a sweatshirt for overnight stays outside.
For the reef, equipment for snorkeling, water shoes or rubber soled shoes.
To visit mosques, you must have covered shoulders and legs, and bare feet.
For women, it is best to avoid shorts and miniskirts in rural and non-tourist areas.