Why you need to worry about the ‘wet-bulb temperature’

A woman covers her baby with a cloth during a hot afternoon on the outskirts of New Delhi, India in May. Photograph: Harish Tyagi/EPA

In March, April and May this year, India and its neighbours endured repeated heatwaves that exposed more than a billion people to dangerously hot conditions. India broke several temperature records. The warmest March in more than a century was recorded across the country and a new high of more than 49C was hit in Delhi in May.

Record-breaking heat has also been recorded elsewhere this year, including the UK, which smashed its previous record by an incredible 1.6C, reaching more than 40C. Portugal reached 47C on the 21st of this month, the hottest July day on record, while several places in France recorded new highs.