Summary Prefabricated temporary houses (PTHs) are extensively used for temporarily accommodation disaster victims. However, the thermal environment inside PTHs can be intolerable in summer. Previous related studies showed the success of applying a movable phase change material (PCM) design to PTHs for improving indoor thermal environments in Chengdu, China; it only represented the “warm temperate‐fully humid‐hot summer” climate. Since various natural disasters may occur around the world, it became necessary to study the effectiveness of applying the movable PCM design to PTHs installed in other climate regions globally. Therefore, following the previous experimental and numerical studies where only one climate condition was considered, in the current article, a numerical study is reported on applying the movable PCM design to PTHs in 12 selected cities in different climate regions to improve their indoor thermal environments in July. The results from the numerical study showed that, in all the 12 selected cities in July, after introducing the movable PCM design to the PTHs, both the maximum indoor air temperature, the monthly averaged air temperature inside the PTHs, the daily peak and daily average indoor air temperature on the hottest day were lowered. It was further demonstrated that on the hottest day in July, the difference between the daily peak air temperature values inside the disaster‐relief PTH with and without incorporating the movable PCM design varied from 2.12°C to 5.34°C, and that between the daily air temperature values varied from 1.53°C to 3.56°C. In all the 12 selected cities, although applying the movable PCM design to disaster‐relief PTHs in July was functional, it was more effective for the following seven cities, that is, Singapore, Miami, Bangkok, Chengdu, Damascus, Hanoi, and Urumqi (with normalΔ values being not less than 300°C·h and normalΔ′ being not less than 46%), with six of the seven cities located in both tropical and temperate climate regions, based on the evaluating criteria proposed in this article.