January in Nagasaki is the coldest month of the year. In January, the weather in Nagasaki is typically cold. Average daily high temperature in January is about 9 degrees above zero. On average, Nagasaki has 10 partly cloudy, 9 rainy, 8 sunny, and 4 cloudy days in January. The rains are usually heavy. January as well as February, June, July, and August is considered the most uncomfortable time to visit Nagasaki.