Due to its location in the Marmara Region, Kocaeli has a climate type influenced by both the Black Sea and the Sea of Marmara. The climate in Kocaeli is typically characterized by a temperate maritime climate. Humidity is high throughout the year and this is especially noticeable in the summer months. Winter months are cold and rainy, while summers are hot and humid. Spring and fall seasons are generally warm and rainy.
The winter months are generally cold and rainy. Average temperatures range between 4°C and 10°C between December and February. During these months, there is heavy rainfall and snowfall can occasionally occur. The spring season, from March to May, is a period when temperatures gradually increase and nature comes to life again. Average temperatures start at 10°C and rise to 20°C in May. Rainfall is also frequent in spring, but is usually short and light.
During the summer months, from June to August, temperatures usually range between 25°C and 30°C. July and August are the hottest months, with temperatures sometimes exceeding 30°C. The high level of humidity further increases the perceived heat, leading to muggy weather at times. In summer, rainfall is less frequent and less abundant, but sudden summer rains can occur.
Autumn, from September to November, is usually mild and temperatures gradually start to drop. In September, temperatures are usually around 20°C, while in November they can drop as low as 10°C. The autumn months are also characterized by frequent rainfall, which is usually prolonged and intense.
Winds in Kocaeli generally blow from the north and northeast directions. These winds increase the effect of cold air waves, especially in winter, and have a cooling effect in summer. This regular breeze of the winds relieves some of the pressure caused by humidity, especially in summer.
Kocaeli's climate has a significant impact on life. High humidity affects comfort levels, especially in summer, while cold and rainy weather in winter increases the need for heating. This seasonal variability affects many aspects of daily life, from clothing to health conditions, transportation to energy consumption. Especially during rainy periods, problems such as flooding can occur, which increases the importance of infrastructure and drainage systems. The winds can contribute to the region's use of renewable energy, especially when assessed in terms of wind energy potential.