January in Hillsboro is the coldest month of the year. In January, the weather in Hillsboro is typically warm. Average daily high temperature in January is about 12 degrees above zero. On average, Hillsboro has 17 sunny, 10 partly cloudy, 3 rainy, and 1 cloudy day in January. The rains are usually light. January as well as June, July, August, and December is considered the most uncomfortable time to visit Hillsboro.