That’s also loaded the dice for wildfires, as blazes behave more erratically and grow harder to battle. States in the south-west have been hammered by dozens of conflagrations this spring, including a ferocious fire in New Mexico that became the worst in the state’s history.

The number of square miles burned so far this year is more than double the 10-year national average, and wildfires have already set records and destroyed hundreds of homes.

A water shortage emergency in southern California has resulted in water restrictions for six million people amid drought conditions. Photograph: Mario Tama/Getty Images
© Provided by The GuardianA water shortage emergency in southern California has resulted in water restrictions for six million people amid drought conditions. Photograph: Mario Tama/Getty Images

Destructive fires, a devastating drought, and torrential floods are each catastrophes in their own right – but when they overlap they are even more capable of causing calamity. Scientists say these events are happening more frequently, and that the climate crisis is a key culprit.

“These are three events that are all extremely consistent with our baseline well-understood expectations of climate change,” said Dr Karen McKinnon, a climate scientist and professor at University of California Los Angeles. She explains how, when the atmosphere warms, it holds onto more moisture. That deepens drought conditions and sets the stage for stronger storms.

“The most basic influence of us putting more greenhouse gasses in the atmosphere is temperatures warming,” she said.  “We can pretty confidently say going forward that these types of events are just going to be more likely because temperatures keep going up and up.”

What we are seeing is we are just going to be getting more and more of these heatwaves breaking records because we are moving temperatures toward warmer conditions

Karen McKinnon

While extreme heat makes other weather events more dangerous, it’s also a deadly threat on its own. Heatwaves have already taken a serious toll this year. Millions of people across the US have faced sweltering springtime temperatures that fail to drop at night, increasing the potential for harm to health. An investigation by the LA Times published last year found that fatalities from heat are abysmally undercounted in California, and that related deaths could be as much as six times higher than the official tally.

“What we are seeing is we are just going to be getting more and more of these heatwaves breaking records because we are moving temperatures toward warmer conditions,” McKinnon said. Scientists say heatwaves are also growing in size, impacting entire regions with greater frequency. Roughly a third of Americans – more than 100 million people – had to grapple with dangerous temperatures as a heatwave covered large swaths of the country last week.

‘Biggest crisis facing our nation’, but can resources keep up?

Compounding catastrophes have put strain on resources. From a severe shortage in firefighters ahead of peak risk periods to difficulty reining in water-use, agencies struggle to prepare for the worst effects. Patrick Roberts, a senior political scientist at the Rand Corporation who studies disasters, says many systems have gotten better at contending with simultaneous events but there’s more work to be done.

Flooding seen in Livingston, Montana. Photograph: William Campbell/Getty Images
© Provided by The GuardianFlooding seen in Livingston, Montana. Photograph: William Campbell/Getty Images

“Covid gave us the experience of a national emergency,” he said, noting that although the pandemic has been dire, it helped streamline national systems that never had to respond simultaneously to an event not confined to a geographical region.

Not preparing comes at a high cost, both financially and in the devastation wreaked on communities.

Every dollar spent on hazard mitigation saves the US $6 in future disaster costs, according to a study released in 2019 by the National Institute of Building Sciences. Last year, the US spent an alarming $145bn on natural disasters – the third highest amount on record – and grappled with 20 extreme events that cost more than $1bn each, close to triple the average since 1980.

The Federal Emergency Management Agency (Fema) is already bracing for an escalation in need this year and for the ones that follow, requesting $19.7bn for its 2023 disaster relief fund.

“The field of emergency management is at a pivotal moment in its history,” Fema administrator Deanne Criswell said during a hearing of the House homeland security subcommittee on emergency preparedness, response and recovery. The agency is managing more than triple the amount of disasters this year as it did a decade ago.

“The changing climate is the biggest crisis facing our nation and makes natural disasters more frequent and more destructive,” Criswell said. “While our mission itself has not changed, our operating environment has.”