In August, the weather in Invercargill is typically warm. Average daily high temperature in August is about 10 degrees above zero. On average, Invercargill has 21 rainy, 4 sunny, 4 cloudy, and 2 partly cloudy days in August. The rains are usually light. August as well as January, March, April, and May is considered the most uncomfortable time to visit Invercargill.