Apparent Temperature-Based Outdoor Heat-Risk Distribution in China

In the context of global climate change, the frequent occurrence of heatwave events not only affects human production activities but also threatens personal safety. From the perspective of human health, this paper uses daily meteorological data of 657 weather stations and remote sensing data from 2000 to 2019 for discussing the distribution of outdoor heat risk during the warm season (May–October) in China based on the apparent temperature index, which considers air temperature, humidity, wind speed, and radiation. Then, the 1-km resolution outdoor heat-risk distribution is mapped. When the results were compared with the results of the high-temperature classification using temperature as a single indicator, it showed that the heat-risk zones based on the apparent temperature were more detailed and consistent with human thermal perception than the risk zones delineated by temperature alone. This will help more outdoor workers who are vulnerable to potential heat risks to anticipate and make better protective measures in advance. First, the heat-risk levels follow the pattern of decreasing from south to north and east to west, as does the number of thermal-risk days. Regions with the highest heat-risk level and longest thermal-risk days include the middle−lower Yangtze River, Guangdong, Guangxi, and Hainan Provinces, with heat-risk days possibly exceeding 140. The number of days with thermal risk ranges from 100–120 days in northern China and 50–90 days in the northern areas. Second, the thermal-risk levels in all provinces peaked in June–August. Moreover, high temperatures can occur locally, and the Turpan region of Xinjiang and the valley of southern Tibet experience different levels of thermal risk throughout the warm season. This study fully considers several elements that affect outdoor thermal comfort. Assigning risk levels can provide guidance to outdoor workers on heat avoidance to decrease their suffering from heat-related injuries. It can also provide a scientific basis for developing more detailed heat subsidy measures in different regions of China.