In December, the weather in Passo Fundo is typically warm. Average daily high temperature in December is about 25 degrees above zero. On average, Passo Fundo has 15 rainy, 12 sunny, 3 partly cloudy, and 1 cloudy day in December. The rains are usually heavy. December as well as January, February, and July is considered the most uncomfortable time to visit Passo Fundo.