weather in istanbul turkey in april
Blue Mosque or Sultanahmet Camii in Istanbul, Turkey. Â© Photo by Ming-yen Hsu Spring. While the astrological spring starts on March 21, in Istanbul spring generally starts somewhere mid-April. The weather becomes warm during the day and pleasantly cool at night, while rain showers are getting rare. You can expect average high temperatures between 18 C (65 F) and 27 C (81 F).