It’s Not (Just) the Heat, It’s the (Steadily Rising) Humidity

Having just spent a few days doing heavy physical farm work in northern Arkansas – can confirm.

Even the corn is sweating.

Washington Post:

The United States and the entire planet are poised to clinch their most humid summer on record, scientists say. The sweltering conditions, which have pushed this year’s heat close to the limits of survivability in some areas and fueled flooding downpours, are part of a long-term increase in humid heat driven by human-caused climate change.

Climate models have long predicted that a warming world would lead to higher humidity, because warmer air evaporates more water from Earth’s surface and can hold more moisture. The consequences of more humid heat include greater stress on the human body, increased odds of more extreme rainfall, warmer nights and higher cooling demand.

With only a few days left in meteorological summer, defined as June to August, this summer is on track to be the most humid in the United States in 85 years of recordkeeping based on observations of dew point — a measure of humidity — compiled by Hudson Valley meteorologist Ben Noll. It’s also likely to end up being the most humid summer globally, Alaska-based climate scientist Brian Brettschneider said in an email to The Washington Post.

If both trends hold, then five of the most humid summers in both the United States and worldwide will have occurred since 1998.

“I have been tracking increasing surface moisture at the monthly time scale. June 2024 and July 2024 both set records for highest dew point for their respective months,” Brettschneider said. “I expect August 2024 to be a record too. Summer 2024 should break the record set in summer 2023.”

This summer’s surge in humidity continues a trend that goes back several decades, with extreme humid heat having more than doubled in frequency since 1979, according to a 2020 study led by UCLA climate scientist Colin Raymond.

Increasing humidity “makes summer heat feel more relentless, with a particular effect on nighttime temperatures,” Raymond said in an email. “That means more demand for cooling, and worse health consequences when cooling is unavailable or unaffordable.”