Arun, United Kingdom offers 15 beaches perfect for sunbathing, surfing, swimming, and more. Arun, England, United Kingdom, is known for Arundel Castle and the South Downs National Park. The best time to travel to Arun, United Kingdom, is during late spring to early summer (May to June) when the average air temperature is around 15-20°C (59-68°F) and the water temperature is approximately 12-15°C (54-59°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!