In the midst of June 2015, the city of Karachi was hit by a heat wave that resulted in 1200 – 2000 deaths and over 50,000 casualties. This burden caught the attention of various stakeholders ranging from government officials to medical responders to mobilize resources for planning a well-designed response. The HEAT manual is among one such efforts to respond to such extreme climatic emergencies. It was designed as part of the Heat Emergency Awareness and Treatment (HEAT) cluster randomized trial, funded by Research for Health in Humanitarian Crisis that assessed the gap in assessment and management of patients who are presenting to the emergency departments (ED) with heat illnesses in low resource settings. This manual incorporates information that was gathered by a systematic review and suggestions from an expert panel comprising of clinicians and researchers from Pakistan and the United States of America. The HEAT Provider Manual was utilized by the investigators to train healthcare personnel in the hospitals that participated in the trial. The material in this manual is intended to provide generic guidelines that can be tailored to the hospital resources and healthcare staff.