Background: Heat stress is considered a well-established phenomenon from extreme heat exposure for long time without taking safety measures. Heat stress is determined by various symptoms, such as fatigue, nausea, vomiting, dizziness, and giddiness. Objective: The current study aimed to assess heat stress exposure among outdoor cleansing workers in Helwan University. Patients and methods: Design: Descriptive research design. Sample: A convenience sample for consists of 100 outdoor cleansing workers that had been worked outdoor in Helwan University, Egypt. Setting: The study was conducted in outdoor at Helwan University. Tools: Data were collected by two tools; the 1st tool included demographic characteristics, workers` knowledge about heat stress, and workers` reported practice regarding heat stress, and the 2nd tool included standardized observational checklist for heat stress risk assessment. Results: Up to 80% of workers were exposed to sun burn and 90% of them were exposed to sun stroke in the last 12 months. Also, they had poor level of knowledge, inadequate reported practices regarding heat stress with highly statistically significant differences between correlation of total knowledge, total reported practice and standardized observational checklist for heat stress risk exposure. There was a highly significance correlation between workers‘total knowledge and workers‘ total reported practice, together with a highly significance correlation between workers‘ total knowledge, workers‘ total reported practice and standardized observational checklist for heat stress risk exposure. Conclusion: Continuous health education program for outdoor cleansing workers regarding prevention of heat stress is essential.