This report reviews the implications of heat stress in working environments in agriculture (with a focus on farming and forestry), how it affects the human body, the risks it poses to human health, how it is measured, how it affects labour productivity, and how it can be managed. Managers often disregard heat stress as an occupational hazard, and workers therefore often have to handle this aspect of the work environment themselves. Heat stress has a negative effect on worker performance, and exposure to severe heat stress can be fatal; nevertheless, it can be greatly reduced with proper work organization and education.