Yes, in 2026, air conditioning is a standard feature on nearly all modern intercity and high-speed trains worldwide. In the UK, newer fleets like the LNER Azuma, Great Western Railway (GWR) Intercity Express, and the recently launched Chiltern Railways modern units all feature climate control. Similarly, in the USA, Amtrak's Acela Express and long-haul Superliner cars are fully air-conditioned to ensure comfort across diverse climates. Across Europe, the ICE (Germany), TGV (France), and Frecciarossa (Italy) consider AC a baseline service. However, a supportive peer warning: some older regional or "commuter" trains in rural parts of Europe and the UK may still lack AC, relying on windows that open. For 2026 travelers, it is always worth checking the specific "train type" on your ticket if you are traveling during a summer heatwave.