She lived her entire life in Jackson, Mississippi, a place that knows hot summers, but she never installed an A/C unit.

As heat wave after heat wave sweeps across the northern hemisphere, many of us choose to fight the heat by huddling in our homes and cranking up the air conditioning.

The problem is, air conditioners don’t make the heat go away. They just shift it out of your home and into the great outdoors. So it gets even hotter out there. In fact, air conditioners produce more heat when they run just like any other powered appliance. That means they send even more heat outside than they take from inside your house. And if you aren’t powering your AC using solar, it’s probably powered by fossil fuels. That’s not good.

The result is that places where many people use A/C become heat islands, especially if they are made of heat-retaining concrete and glass.

Bloomberg recently highlighted a collaboration between the European Space Agency, NASA, and the U.S. Geological Survey on passive methods that cities use to cool public areas.

The most effective is also the lowest tech–trees. The EPA is a big proponent of using trees in urban environments to increase air quality and lower temperature. One of the things we love most about the new Inflation Reduction Act is its $1.5 billion investment in urban forestry.

Pavement makes up between 35-50% of the area of a city, and we all know that scorching hot walk across a big parking lot during the dog days of summer. The heat just radiates up through the soles of your shoes. On a hot day, asphalt can get as high as 140 degrees.

The Moroccan desert city of Fez can get blistering hot, but one of its coolest neighborhoods is also one of its lowest-income neighborhoods. The Seffarine District’s narrow, unpaved streets and tall clay-brick buildings keep the area as much as 8 degrees celsius cooler than its surrounding areas.

Seville, Spain, has tapped into the wisdom of the ancients, using a millennia-old Iranian water-cooling method on Cartuja Island. Qanats. These underwater aqueducts will funnel cool water from the Guadalquivir river through nearby buildings where it will cool the ambient temperature by up to 10 degrees Celsius. In a twist on the ancient technology, cool water will run through the walls of buildings to cool the air. There will even be chilled benches in the area for pedestrians to rest on. How cool is that?