Special report: Rising heat
Can we cool the risks of an invisible disaster?
By Laurie Goering
When Hurricane Harvey blasted ashore in August, drowning south Texas in a year's worth of rain in just a few days, it left behind an estimated $150 billion in damage to sodden homes and inundated factories, and claimed about 60 lives.
Two weeks later, Hurricane Irma churned into Florida, killing at least 33 people there and causing billions more in damages - as well as brutal loss of life in the Caribbean.
But the storms may not be 2017's deadliest U.S. disaster. Instead, that title may go to a largely unseen killer: rising temperatures.
Over the last 30 years, increasingly broiling summer heat has claimed more American lives than flooding, tornadoes or hurricanes, according to the U.S. National Weather Service.
And the problem has not been limited to the United States. More than 35,000 people died during a European heatwave in 2003, and tens of thousands perished in Russia during extreme heat in 2010.
The threat is particularly severe in already sweltering places, from South Asia to the Gulf, and has been linked to a rise in migration out of hot and poor parts of rural Pakistan.
But experts say heat remains underestimated as a threat by governments, aid agencies, and individuals. That's both because it's an invisible, hard-to-document disaster that claims lives largely behind closed doors - and because hot weather just doesn't strike many people as a serious threat.
"If you have a natural disaster like a cyclone or an earthquake or a flood, the impacts are immediate. Things get washed away, people drown. But heat is a silent killer," said Sarah Perkins-Kirkpatrick, a climate change researcher at Australia's University of New South Wales.
"In Australia, heatwaves kill more people than any other natural disaster - but no one realises the destruction they can cause. The attitude is, 'It's hot, suck it up, get on with it'."
Around the world, heat is a neglected and poorly understood disaster, in part because few of the deaths it produces are directly attributed to heatwaves.
Victims - many elderly, very young, poor or already unhealthy - often die at home, and not just of heat stroke but of existing health problems aggravated by heat and dehydration.
In India, for instance, a major risk factor for women - who die of heat far more often than men, researchers say - is the lack of an indoor toilet.
To avoid embarrassment or harassment, many women refrain from drinking water during the day to limit their trips to the toilet - a potentially deadly strategy during heatwaves.
"These deaths are recorded as normal deaths. But they wouldn't have happened if it wasn't so hot," said Gulrez Shah Azhar, an Indian heat researcher who works for the RAND Corporation, a global think tank.