In September, the weather in Llandudno is typically warm. Average daily high temperature in September is about 14 degrees above zero. On average, Llandudno has 22 rainy, 4 cloudy, 3 sunny, and 1 partly cloudy day in September. The rains are usually heavy. September as well as January, February, March, and April is considered the most uncomfortable time to visit Llandudno.