While the modifying effects of a city's surface on its climate are well doc
umented, there remains a need for useful micro-scale analyses of thermal co
mfort conditions which may be applied to urban design. In the present study
, empirical data taken from extensive full-scale measurements in a number o
f low-rise urban street canyons in the arid Negev region of Israel are inte
grated with an energy-balance model representing the thermal exchanges betw
een a pedestrian and the street canyon environment. Analysis of microclimat
ic parameters and overall energy balance suggests that in summer, overheati
ng within the canyon is sensed primarily as a nocturnal phenomenon, and tha
t during hours of substantial heat stress in a desert climate, the compact
canyon is in fact a potential "cool island", mainly due to internal solar s
hading. In winter, a compact geometry was found to provide relatively warm
conditions, with the key Factor being protection from strong winds during c
old night hours. (C) 1999 Elsevier Science Ltd. All rights reserved.