What should you know about hot humid weather and fatigue?

Humidity slows sweat evaporation, so the body works harder to release heat. Sweating also removes fluid and salts, and mild Dehydration can leave you tired, headachy or light-headed. Poor sleep in a warm room can add to daytime fatigue. If tiredness occurs away from hot weather or lasts despite rest and hydration, consider other explanations such as Anaemia, Coeliac Disease, COVID-19, Burnout or Chronic Fatigue Syndrome. Chronic Kidney Disease and Alcohol Use Disorder can also contribute to low energy. Fatigue is a symptom, so its pattern and accompanying signs matter.

Plan demanding activity for cooler parts of the day and take regular breaks in shade or air conditioning. Drink regularly, eat normally, and replace fluids after heavy sweating; follow medical advice if you have a condition that limits fluid intake. Choose light clothing and keep the sleeping area cool. Avoid relying on alcohol to relax or sleep. If fatigue persists, keep a brief record of sleep, heat exposure, fluids, medicines and other symptoms for your clinician.

Move to a cool place and seek urgent help for confusion, fainting, seizures, severe breathlessness, chest pain, or skin that is very hot with a change in behaviour. Get prompt advice for persistent vomiting, inability to drink, very little urine, severe dizziness, or worsening weakness. Fatigue with black stools, unusual bleeding, yellow skin or new neurological symptoms also needs medical assessment.

Ask whether your fatigue pattern suggests dehydration, a sleep problem, infection, anaemia or another condition. Discuss medicines, alcohol, diet, menstrual or other blood loss, and whether blood or urine tests would be useful.