Making cities and farm fields more reflective - including by painting buildings white or leaving more land unploughed after harvests - could reduce extreme heat by up to three degrees Celsius in areas where the techniques are used, scientists say.
While such measures would not lower global temperatures such simple changes could provide substantial local or regional relief on the hottest days, according to research in the journal Nature Geoscience.
"This is clipping the upper tail of extreme temperatures," said Andy Pitman, director of the ARC Centre of Excellence for Climate Extremes at University of New South Wales, Australia one of the countries struggling with blistering hot days.
The measures could mean fewer heat deaths in cities during scorching weather and fewer threats from everything from heat-warped rail lines to electrical outages from excess demand for electricity, said Pitman, one of the authors of the study.
"If you can bring the extreme temperature down a degree or two you reduce the risks. And that might mean you don't trigger the brownout - or a human health catastrophe," he said.
Painting homes white - something common across parts of the Mediterranean, for example - is hardly a new idea to combat heat. "Italians and Greeks worked this out a thousand years ago," Pitman noted.
Many other parts of the world may need to "rediscover what some countries or populations have done for a long time", he said.
On farms, leaving fields unploughed after harvest to increase the amount of sunshine they reflect, could also help lower local temperatures, said Sonia Seneviratne, the study's lead author and an expert on land and climate dynamics at ETH Zurich, a Swiss university.
Changing the types of crops planted - or developing ones designed to reflect more light from their leaves, potentially using genetic modification - also could help, she said.
With the world struggling to hold global temperature increases to below two degrees Celsius above pre-industrial times, in line with the Paris Agreement on climate change, such measures could provide a fairly benign way to cut risks from rising heat, Seneviratne added.
The report noted that modifying the reflectivity of cities and farm fields appears to work best in North America and Europe, where it has no clear negative side effects.
In parts of Asia, however, where contrasts between land and sea temperatures help drive monsoon rains, changing local temperature extremes might have some impact on monsoons, the report warned.
Pitman said the findings do not mean that "someone should take a paintbrush and wander over all the Earth's cities painting them white".
Instead, as cities renovate and build new infrastructure, they should "consciously make the city brighter".
