The best time to go to Ystradgynlais is during the late spring to early autumn months, specifically from May to September.This period offers the most agreeable weather for exploring the Brecon Beacons National Park, which Ystradgynlais borders. You'll find warmer temperatures and less rainfall, making outdoor activities like hiking, cycling, and exploring the local waterfalls more pleasant. The days are also longer, giving you more daylight hours to enjoy the scenery.For couples looking for an active holiday, these months are ideal for enjoying the numerous walking trails in the area, such as those leading to Henrhyd Falls, the tallest waterfall in South Wales. The local pubs and cafes are also more inviting with outdoor seating when the weather is fine.Families will also find this time of year great for outdoor adventures. The nearby National Showcaves Centre for Wales, with its dinosaur park and underground caves, is best enjoyed on a dry day.