Hot weather can trigger diarrhea through dehydration, spoiled food, or heat-related illness. Staying hydrated, eating light foods, and storing food safely help prevent heat-related diarrhea. Heat-Related IllnessesHeat-related illnesses, like heat stroke or heat exhaustion, may cause or contribute to diarrhea. Chronic (long-term) health conditions may cause diarrhea or influence how your body manages its fluids, such as:Some prescribed medications may also affect fluid retention or cause loose stools as a side effect. Consider these self-care tips for managing diarrhea caused by heat:Replenish fluids: Dehydration is a common side effect of diarrhea.