The Rocky Mountaineer carriages are fully temperature-controlled with modern air conditioning and heating systems, so the interior remains comfortable regardless of the weather outside. However, the perceived temperature can vary depending on your service level and activity. In GoldLeaf Service, the bi-level glass-domed coaches provide a sun-drenched upper level that can feel warm on bright days, while the lower dining area may feel cooler. In contrast, the outdoor viewing platforms (available in both service levels) will be significantly colder due to the wind chill of the moving train and the high-altitude mountain air. Even in mid-summer, the temperature in the Canadian Rockies or the high Colorado desert can change rapidly. Travel experts recommend dressing in layers and bringing a light sweater or jacket; this allows you to step outside to capture photos of the scenery without freezing, while staying cozy once you return to your seat.