Mumbai set to become hotter by 2100: Study

The study projects that globally the number of mild days will decrease by 10 or 13 per cent by the end of the century because of climate warming from the buildup of human-caused greenhouse gases in the atmosphere.

The current global average of 74 mild days a year will drop by four days by 2035 and 10 days by 2081 to 2100.

However, this global average decrease masks more dramatic decreases in store for some areas and increases in mild days in other regions.

Scientists defined "mild" weather as temperatures between 18 and 30 degrees Celsius, with less than a half inch of rain and low humidity.

Knowing the general pattern for mild weather over the next decades is also economically valuable to a wide range of businesses and industries, researchers said.

Travel, tourism, construction, transportation, agriculture, and outdoor recreation all benefit from factoring weather patterns into their plans, he said.

"Extreme weather is difficult to relate to because it may happen only once in your lifetime," said first author Karin van der Wiel, a postdoctoral researcher at NOAA's Geophysical Fluid Dynamics Laboratory (GFDL).

"We took a different approach here and studied a positive meteorological concept, weather that occurs regularly, and that's easier to relate to," said van der Wiel.

Scientists predict the largest decreases in mild weather will happen in tropical regions because of rising heat and humidity.

The hardest-hit areas are expected to be in Africa, Asia and Latin America, where some regions could see 15 to 50 fewer days of mild weather a year by the end of the century.