LOS ANGELES — As the second record-breaking heat wave of the season seizes the Southwest, experts warn that this summer's historic hot spells are digging into America's pocketbook.

"The biggest impact on the economy is the human toll associated with heat-related mortality and illness," said Alex Barron, assistant professor of environmental science and policy at Smith College.

High temperatures Tuesday broke daily records in parts of Southern California, where Death Valley hit 127 and Palm Springs reached 121, according to the National Weather Service. Phoenix's high (116) matched its record for the date. Experts say the odds are that these heat spells ― increasing in frequency and intensity ― are connected to long-term climate change.

"Global warming has put a very strong thumb on the scales," said Noah Diffenbaugh, a professor of earth system science at Stanford University. "Not every record heat event is influenced by global warming, but we’re getting close to that point."

When the physically vulnerable and frail fall ill as a result of heat spells, it affects health care spending, which already takes up nearly one-fifth of the American economy. The Natural Resources Defense Council, an environmental advocacy group, found the health-related costs of heat waves for much of the last decade reached $5.3 billion.

A recent study in the journal Nature Climate Change concluded that there's a strong correlation between rising temperature and increased suicide rates in the United States and Mexico.

Another heat-wave impact is that electricity becomes pricier as demand rises. Utility customers can spend billions of extra dollars during extreme weather events. "Heat waves increase cooling demands, thereby boosting electricity consumption to its highest value and testing the ability of the system to meet this demand," states a Spanish university study from 2017.

Worker productivity decreases during heat waves. Studies show the slowdown is particularly acute in outdoor industries such as construction, but experts say even office workers take it easier on scorching days.

"When it’s really hot outside your first hour in the office is significantly less productive," said Trevor Houser, co-director of the Climate Impact Lab.

Farm states, California principally among them, can experience devastating crop losses due to scorching temperatures. A 2016 study from a University of British Columbia researcher found that drought and heat waves knocked out nearly a tenth of the world's cereal production between 1964 and 2007.

"Not only are crops suffering, but the people harvesting them are also suffering," said Barron, of Smith College. "It has a real human cost."

Even tourism is affected when planes are grounded because it's just too hot to fly. Last week aircraft maker Bombardier announced that the Federal Aviation Administration is now allowing two of its models to take off when it's as hot as 122 degrees on the ground.

The knowledge that extreme heat costs everyone, and that it's likely to intensify in the years to come, means that governments will have to plan to spend more.

"A lot of our systems and infrastructure were built for an older climate," says Stanford's Diffenbaugh. "The good news is we have opportunities to catch up and get ahead."