Cities are overheating. How do we cool them down?

It's getting hot in here, especially if you live in a big city, as most Canadians do. And with cities getting warmer than ever, experts say it's time to make our cities cooler. 

"I think all of the answers exist right on our doorsteps, and we just have to work together to make it happen," said Melissa McHale, an associate professor of urban ecology at the faculty of forestry at the University of British Columbia in Vancouver. 

The warming planet means heat waves will be more intense and more frequent, and that heat is amplified in cities, due to the urban heat island effect.

That's the name given to describe when cities trap and radiate heat, making them several degrees warmer than the surrounding countryside.

"Much of this higher temperature is because of the fact that urban areas tend to have surfaces like concrete and asphalt," said Sandeep Agrawal, a professor at the School of Urban and Regional Planning and the director of the Alberta Land Institute at the University of Alberta in Edmonton.

"They absorb a lot of solar energy, and then they release it in the air over time."

But it's not just those surfaces. Big buildings, packed closely together block the wind and trap the heat.

While the solutions take time, says McHale, there are changes that can be made to cool cities down.

Agrawal and his team studied temperatures in Toronto, Vancouver, Edmonton, Calgary and Montreal using satellite images that record land surface temperatures in the cities and surrounding rural areas. 

He found that urban areas were often six to 12 degrees hotter than rural areas, with the highest urban heat islands in Toronto and Vancouver. 

Agrawal says there needs to be more trees which absorb heat over time, and less concrete. He also suggests larger buildings have what are called green roofs, which would have vegetation or water to reflect and soak in some of that heat. 

Agrawal says some municipalities are making strides. He says Toronto has enacted strong protections around the cutting down of trees, as well as the implementation of green roofs. 

James Voogt, a professor of geography and environment at Western University in London, Ont., says it's pretty clear that these are important issues for cities to tackle.

"If you look at all of the environmental factors, I like to call them the ways that weather can kill you, heat is number one," said Voogt. "It's been underreported in the past but it's of growing concern."