Abstract: Based on the daily data from 143 national-level surface meteorological observation stations in Hebei Province during the summer months from 1991 to 2020,as well as the daily data from 8 radiation stations from 2014 to 2020,this study takes the Universal Thermal Climate Index (UTCI) as the evaluation indicator.It reveals the spatiotemporal distribution pattern of summer human thermal comfort using trend analysis and Kriging interpolation methods.The results show that over the past 30 years,the proportion of comfortable days in Hebei Province during summer has generally shown a decreasing trend,with a trend value of -0.9% per decade.There are spatial differences: as the altitude decreases,the tendency rate of the proportion of comfortable days shifts from positive to negative.The proportion of comfortable days in plains,hills,and low mountainous areas presents a single-valley pattern,while high-altitude areas show a single-peak pattern.The number of summer comfortable days in these four types of terrain is 24,81,92,and 92 days respectively,with low mountainous and high-altitude areas having comfortable days throughout the entire summer season.In terms of spatial distribution,there is an overall decreasing trend from northwest to southeast.High-altitude areas have the highest proportion of comfortable days,reaching 95.6%,while plains have the lowest proportion at 33.8%.High-altitude areas have the highest proportion of comfortable days in July and August.However,in June,due to the still relatively low temperatures in high-altitude areas,low mountainous areas have the highest proportion of comfortable days.Therefore,low mountainous and high-altitude areas in Hebei Province have a comfortable summer thermal sensation and are suitable for traveling.The plains are suitable for traveling in the first and middle ten days of June,and the hills are suitable for traveling except in the last ten days of July.

Key words: Universal Thermal Climate Index (UTCI), Human Comfort, Comfort Level Percentage