In terms of precipitation, rainfall in Istanbul ranges from 0.4 - 3.9 inches per month. December is typically the wettest month, when rainfall can reach 3.9 in. July is typically the driest time to visit Istanbul when rainfall is around 0.4 in.
If weather is an important factor for your trip to Istanbul, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 73.4 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 41.0 F).