AbstractUrbanization is known to disrupt the surface energy balance of an urban area. The phenomenon of higher temperatures and thermal discomforts within a local urban setting is broadly known as the Urban Heat Island (UHI) effect. This research employed roadside temperature measurements to examine microclimate UHI variation in Mongkok, a small urban community of Hong Kong. Results of the spatio-temporal examination indicated diurnal and seasonal variations in the microclimate. A five-level index named the “UHI Threat Rating” was devised to offer easy interpretation of the microclimate UHI variations and facilitate identification of temperature hotspots within a small urban community.