Department of Nutrition, Exercise and Sports, Section for Integrative Physiology, University of Copenhagen, Copenhagen N, Denmark. morris@nexs.ku.dk. Thermal Ergonomics Laboratory, Faculty of Medicine and Health, University of Sydney, Sydney, Australia. FAME Laboratory, School of Exercise Science, University of Thessaly, Thessaly, Greece. Federal Office of Meteorology and Climatology, MeteoSwiss, Zurich Airport, Zurich, Switzerland. Meteorology Group, Department of Applied Mathematics and Computer Sciences, University of Cantabria, Santander, Spain. Thermal Environment Laboratory, Division of Ergonomics and Aerosol Technology, Department of Design Sciences, Faculty of Engineering, Lund University, Lund, Sweden. Environmental Ergonomics Research Centre, Loughborough Design School, Loughborough University, Loughborough, UK. Department of Nutrition, Exercise and Sports, Section for Integrative Physiology, University of Copenhagen, Copenhagen N, Denmark.