August in San Cristobal de las Casas is the rainiest month of the year. In August, the weather in San Cristobal de las Casas is typically warm. Average daily high temperature in August is about 22 degrees above zero. On average, San Cristobal de las Casas has 31 rainy days in August. The rains are usually heavy. August as well as May, June, July, and September is considered the most uncomfortable time to visit San Cristobal de las Casas.