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Monthly averages for İstanbul from the Turkish State Meteorological Service, measured over 1950–2025.
The warmest month is July, with an average high of 29.7 °C. The coldest is January, when the average low is 4.2 °C. January has the most rainy days (16.3 on average), and July the fewest (3.5).
Month by month
| Month | Avg high °C | Avg low °C | Rainy days |
|---|---|---|---|
| January | 9.6 | 4.2 | 16.3 |
| February | 10.2 | 4.2 | 13.9 |
| March | 12.4 | 5.5 | 12.6 |
| April | 17.4 | 9.2 | 10.1 |
| May | 22.3 | 13.6 | 7.5 |
| June | 27.1 | 18 | 5.4 |
| July | 29.7 | 20.5 | 3.5 |
| August | 29.7 | 20.8 | 3.6 |
| September | 25.9 | 17.6 | 5.5 |
| October | 20.6 | 13.7 | 9.5 |
| November | 16.1 | 9.9 | 11.3 |
| December | 11.8 | 6.5 | 15.5 |
January
In January, İstanbul averages a high of 9.6 °C and a low of 4.2 °C, with about 16.3 rainy days.
February
In February, İstanbul averages a high of 10.2 °C and a low of 4.2 °C, with about 13.9 rainy days.
March
In March, İstanbul averages a high of 12.4 °C and a low of 5.5 °C, with about 12.6 rainy days.
April
In April, İstanbul averages a high of 17.4 °C and a low of 9.2 °C, with about 10.1 rainy days.
May
In May, İstanbul averages a high of 22.3 °C and a low of 13.6 °C, with about 7.5 rainy days.
June
In June, İstanbul averages a high of 27.1 °C and a low of 18 °C, with about 5.4 rainy days.
July
In July, İstanbul averages a high of 29.7 °C and a low of 20.5 °C, with about 3.5 rainy days.
August
In August, İstanbul averages a high of 29.7 °C and a low of 20.8 °C, with about 3.6 rainy days.
September
In September, İstanbul averages a high of 25.9 °C and a low of 17.6 °C, with about 5.5 rainy days.
October
In October, İstanbul averages a high of 20.6 °C and a low of 13.7 °C, with about 9.5 rainy days.
November
In November, İstanbul averages a high of 16.1 °C and a low of 9.9 °C, with about 11.3 rainy days.
December
In December, İstanbul averages a high of 11.8 °C and a low of 6.5 °C, with about 15.5 rainy days.
Sources
Meteoroloji Genel Müdürlüğü — İstanbul (1950–2025) (opens in a new tab)