In May, the weather in Invercargill is typically warm. Average daily high temperature in May is about 11 degrees above zero. On average, Invercargill has 25 rainy, 3 sunny, 2 cloudy, and 1 partly cloudy day in May. The rains are usually heavy. May as well as January, March, April, and June is considered the most uncomfortable time to visit Invercargill.