The best time to visit Llanberis is during the late spring, summer, and early autumn months, from May through October, when the weather is generally mildest and most conducive to outdoor activities.During these months, you'll find the most reliable conditions for hiking and exploring the Snowdonia National Park. The days are longer, and temperatures are more comfortable for activities like ascending Mount Snowdon. This period also sees all major attractions, such as the Snowdon Mountain Railway and Electric Mountain, operating at full capacity.For those looking to avoid the busiest crowds while still enjoying pleasant weather, late spring (May-early June) and early autumn (September-October) are ideal.