Background Natural ecosystems, such as forests and grasslands, can mitigate heat waves, but research on heat wave mitigation in mountain ecosystems is lacking. Considering the upper reaches of the Yangtze River basin (URYB) as the study area, we first divided the URYB into mountainous and non-mountainous areas based on a digital elevation model (DEM). Then, we used temperature to identify heat waves and used the temperature and humidity index to identify suitable days. Finally, the differences between mountainous and non-mountainous areas were compared, and regional development strategies are proposed. Result (1)The frequency and duration of heat waves increased by 0.433/y (P < 0.1), 0.07/y (P < 0.05), while the number of suitable days in June, July, and August gradually decreased slightly by 0.0096/y (P < 0.1), 0.0125/y (P < 0.1), 0.004/y (P < 0.1), respectively from 1986 to 2015. (2)The average monthly number of suitable days was the highest in mountainous areas during the summer from 1986 to 2015. Mountainous areas have an advantage in mitigating heat waves owing to landform-based changes in the local climate. (3)In addition to the landform, altitude was the main factor responsible for mitigating heat waves in mountainous areas. Conclusion Parts of the plateau and whole mountain areas were found to be best for avoiding extremely high temperatures based on the number of suitable summer days from 1986 to 2015. We suggest formulating tourism promotion strategies, and strengthening tourism infrastructure, considering landscape protection and creation to promote sustainable regional development.