January in Siem Reap is the sunniest month of the year. In January, the weather in Siem Reap is typically hot. Average daily high temperature in January is about 29 degrees above zero. On average, Siem Reap has 16 partly cloudy, 9 sunny, 5 cloudy, and 1 rainy day in January. The rains are usually heavy. January as well as December is considered the most comfortable time to visit Siem Reap.