Aberystwyth's coastal position brings Atlantic weather — mild, damp, and changeable year-round. Summers are rarely hot but can be pleasantly warm, with July and August seeing the most settled weather. The town fills noticeably in school holidays, when the seafront and promenade get as busy as they ever get. Accommodation books up fast in August.
Spring and early autumn are arguably the best times to visit. The weather is unpredictable but the crowds are thinner, and the surrounding countryside — particularly the Rheidol Valley and the uplands above Devil's Bridge — is at its most atmospheric. The Vale of Rheidol Railway runs a full timetable from Easter through October.
Winter is quiet but not unpleasant. The seafront has a certain austere appeal in rough weather, the university keeps the town alive through term time, and several of the main attractions — the National Library, the Ceredigion Museum, the castle ruins — are accessible year-round. The cliff railway closes in winter months.