Weather in Istanbul

On this site the months that score closest to a 22°C day, lighter rain, and moderate humidity are June, July, and August. Istanbul is in Turkey at 41.0°N. The 2001–2020 NASA POWER daily record describes a Mediterranean pattern: dry summers and wetter winters.

August is the warmest month (average 25.7°C, high 29.3°C) and January is the coolest (average 6.0°C, low 3.6°C). Rain is wet season runs from December to January, inside an annual total of 625 mm. The wettest month is December at 82 mm; the driest is July at 20 mm.

How warm Istanbul gets

Monthly average highs run from 8.3°C in January to 29.3°C in August. Nights follow the same curve: 3.6°C in January and 22.2°C in August.

Across the year the mean afternoon high is 18.5°C. If you want the smallest day–night shock, look at months where the high and low sit close together; August nights still hold 22.2°C.

Rainfall pattern

The wet season in Istanbul starts in December and ends in January (December and January). December is the core of it at 82 mm. July is the other extreme, with 20 mm.

Humidity peaks near 84%. That usually lines up with the wetter months rather than the hottest ones.

Distinctive months in Istanbul

By January the wet season is ending. Istanbul still sees about 79 mm, but the next month is usually leaner. March: 11.9°C high, 5.7°C low, 53 mm rain, 79% humidity. April stands apart from the months beside it: 15.9°C / 8.7°C and 42 mm. May brings 36 mm and 7 rainy days; temperatures run from 13.9°C to 21.2°C. In June, Istanbul averages 26.0°C by day and 18.7°C at night, with 36 mm of rain. July is the driest month, averaging only 20 mm across 4 rainy days. Highs sit near 28.9°C.

Peak heat arrives in August: 29.3°C by day, 22.2°C at night, and 66% humidity. September brings 54 mm and 7 rainy days; temperatures run from 19.0°C to 25.4°C. October: 20.1°C high, 14.5°C low, 70 mm rain, 76% humidity. In November, Istanbul averages 15.1°C by day and 9.9°C at night, with 63 mm of rain. The wet season opens in December. Expect 82 mm and 12 rainy days, with nights around 5.7°C.

When the score favours a visit

The three months with the highest comfort score are June, July, and August: June (22.3°C average, 36 mm, 69% humidity); July (25.2°C average, 20 mm, 66% humidity); August (25.7°C average, 22 mm, 66% humidity). They fall in calendar order. The score rewards averages near 22°C, lower rainfall, and humidity near 60%. It is a climate score, not a festival or price calendar.

If you want the wet season itself — fewer crowds, greener landscape, heavier rain — aim at December–January instead of the score.

Istanbul and other cities in Turkey

Bursa is about 91 km away: Istanbul is 1.3°C warmer than Bursa in its hottest month and a similar annual rainfall (642 mm in Bursa). Bursa’s wettest month is December (90 mm) versus December here.

İzmir is about 328 km away: Istanbul is 2.0°C cooler than İzmir in its hottest month and a similar annual rainfall (646 mm in İzmir). İzmir’s wettest month is January (130 mm) versus December here.

Ankara is about 352 km away: Istanbul is 3.1°C warmer than Ankara in its hottest month and 206 mm wetter over the year than Ankara. Ankara’s wettest month is May (51 mm) versus December here.