January in Iwaki is the sunniest and the coldest month of the year. In January, the weather in Iwaki is typically cold. Average daily high temperature in January is about 4 degrees above zero. On average, Iwaki has 13 sunny, 11 partly cloudy, 6 rainy, and 1 cloudy day in January. The rains are usually moderate. January as well as February, March, April, and June is considered the most uncomfortable time to visit Iwaki.