Heat illness often starts small: dizziness on a hot afternoon, a wave of nausea, a cramp, an odd weakness that a cold drink does not fix. On a brutal day, in a poorly ventilated room or out in the sun, those small signs mean the body is losing a fight it usually wins.
Extreme heat forces the body to work harder to stay cool through sweating and blood flow to the skin, and when the air is very hot, humid or poorly ventilated, these systems fall behind. Dehydration develops, and the World Health Organization notes that heat can also worsen heart, lung and kidney conditions.
Heat exhaustion brings heavy sweating, weakness, dizziness, headache, nausea, cramps or fainting, and the response is to move to a cooler place, rest and take fluids if the person can drink. Heatstroke is the dangerous stage, with confusion, collapse, seizures, very high body temperature or hot skin, and it needs urgent medical help without delay.
Outdoor workers, older adults, children, pregnant people and those with chronic conditions face higher risk, as do people taking certain medicines for blood pressure, fluid retention, diabetes or mental health. Research from India, summarised in a health review, links heat exposure to more illness and hospital admissions, making it a serious occupational hazard for those who cannot choose when they work.
Start drinking water early, wear light loose clothing, and avoid strenuous work during the hottest hours where possible, while employers should provide drinking water, shade and regular breaks. Never leave a child, older person or animal in a parked vehicle, and check on older neighbours who live alone during a heatwave.