Creating climate shelters is one of the actions that some cities are implementing to adapt to summer heat waves, increasing in magnitude and frequency due to climate change. These shelters are thought to serve mainly those parts of the city where urban heat islands are more intense and most vulnerable individuals, such as children, the elderly etc., are living. However, the catchment areas of these shelters are generally identified as the 15-min walking isochrones around them, without considering how walking speed can change depending on age and heat. This article proposes a methodology to improve the definition of the shelter isochrones by calculating the actual walking speed of 65-year-old women on a summer day. The methodology is tested on the case study of the Italian city of Turin. The results show how much the share of Turin’s residents who can walk to at least one climate shelter in 15 min changes when age and heat are considered as factors influencing the speed and route choices in travelling to these shelters. Neglecting these factors’ influence may result in a 100% overestimation of the actual number of women over 64 y.o. served.