April in Bialystok is the sunniest month of the year. In April, the weather in Bialystok is typically warm. Average daily high temperature in April is about 12 degrees above zero. On average, Bialystok has 10 rainy, 9 sunny, 8 partly cloudy, and 3 cloudy days in April. The rains are usually moderate. April as well as January, February, March, and October is considered the most uncomfortable time to visit Bialystok.