Shading the Whole Journey: A Review of Outdoor Heat, Ground Surfaces and Climate-Specific Cooling for Sustainable Mega-Event Precincts in Saudi Arabia

Abstract

Saudi Arabia will host World Expo 2030 in Riyadh and the FIFA World Cup 2034 in five cities. Visitors to both events will spend much of their time outdoors: walking from transit stations, standing in security and ticket queues, and gathering in plazas and fan zones at fixed times that cannot move with the weather. Anyone who has walked across an open plaza in a Saudi summer, or even in October, knows that the problem is not only hot air. The sun strikes from above, and a hot, bright pavement sends heat and glare back from below. This review brings together published evidence on outdoor thermal comfort in hot climates and reads it from the point of view of an architect designing the visitor’s route. The main findings are four. First, daytime heat stress in hot-dry cities comes mainly from direct and reflected sun. Continuous shade along the whole visitor journey therefore matters more than any other single measure, and artificial shade can work as well as tree shade. Second, light and highly reflective paving in open sun can lower surface temperature while raising the radiant load on people; reflective surfaces belong under shade, not in exposed plazas. Third, fine water mist works well in dry Riyadh but adds discomfort in humid coastal hosts such as Jeddah and Al Khobar, where cooled and dehumidified refuges and breeze-aware layouts are needed instead. Fourth, standing still in a queue under the midday sun is a heavier burden than walking, and clear information about remaining time and distance helps people tolerate the route. The paper proposes three checks to be passed before an event precinct is approved: shade continuity at the peak hour, maximum exposure time between refuges, and a city-specific assessment of cooling measures using the Universal Thermal Climate Index. Sustainability links include solar canopies that shade and generate power, irrigation with treated wastewater, and targeted rather than blanket active cooling. A short research agenda closes the paper.