August in Niagara Falls is the sunniest month of the year. In August, the weather in Niagara Falls is typically warm. Average daily high temperature in August is about 24 degrees above zero. On average, Niagara Falls has 16 sunny, 8 rainy, and 7 partly cloudy days in August. The rains are usually moderate. August as well as September is considered the most comfortable time to visit Niagara Falls.