WASHINGTON, Aug. 1 (Xinhua) -- Dry months are getting hotter in large parts of the United States, a sign that human-caused climate change is forcing people to encounter new extremes, according to a study published on Wednesday in Science Advances.

Researchers at the University of California (UCI), Irvine reported that temperatures during droughts had been rising faster than in average climates in recent decades.

They described concurrent changes in atmospheric water vapor as a driver of the surge.

"Available soil moisture can remove surface heat through evaporation, but if the land is dry, there is no opportunity to transport it away, which increases the local temperature," said the paper's lead author Felicia Chiang, a UCI graduate student in civil and environmental engineering.

The researchers analyzed temperature and precipitation data from the early and late 20th century and discovered that regions undergoing droughts warmed more than four times faster than areas in the southern and northeastern United States with average weather conditions.

These changes pointed to a greater number of droughts and heat waves co-occurring, which could lead to such calamities as wildfires and loss of crop yields.

Widespread fires caused by abnormally high summer temperatures are currently burning around the world, including in parts of California, Scandinavia and Greece.

"Heat waves and droughts have significant impacts on their own, but when they occur simultaneously, their negative effects are greatly compounded," said the paper's co-author Amir AghaKouchak, UCI associate professor of civil and environmental engineering.

"Both phenomena, which are intensifying due to climate warming, are expected to have increasingly harmful consequences for agriculture, infrastructure and human health," said AghaKouchak.