September in Buenos Aires is the windiest month of the year. In September, the weather in Buenos Aires is typically warm. Average daily high temperature in September is about 17 degrees above zero. On average, Buenos Aires has 13 sunny, 10 partly cloudy, 6 rainy, and 1 cloudy day in September. The rains are usually light. September as well as May, June, and July is considered the most uncomfortable time to visit Buenos Aires.