Things are getting HOT!

Urban Heat Islands Increase the Effects of Climate Change

by Emily Seang, SLCgreen intern

On a hot summer day, it feels like heat is coming from everywhere and anything.

We’ve had a lot of those days lately.  In fact, July of 2018 was the fifth hottest on record (July 2017 was the hottest!)

The National Weather Service, Salt Lake City office, has calculated our July 2018 temperatures as being the fifth warmest on record.

There’s no question that temperatures are climbing as a result of climate change.

In cities, however, there’s also another factor at work.

While we search for some place to cool down, let’s think about what is going on here: Cities have a plethora of paved and built structures (all that asphalt, concrete, steel, brick, and other material) that absorb a lot of heat during the day.  Then, they continue to exude that heat throughout the evening after the sun has gone down.

That’s why, compared to rural areas, cities are significantly hotter than surrounding areas since they are more likely to trap in heat. This, my friend, is what we call the urban heat island (UHI) effect.

Image Source: metlink.org

With climate change exacerbating Salt Lake’s extreme weather, the amount of paved areas and built structures can gradually increase the heat in our already hot cities. Since the 2000s, Utah’s climate has shifted and we have already started to see high annual average temperatures recur year after year.

SLC Annual Average Temps

2012: 56.5 F

2015: 56.3 F

2016: 56.2 F

2017: 56.1 F

In addition to measuring these surface temperatures, the U.S. Environmental Protection Agency (EPA) also considers air temperature, daily temperature, and seasonal temperature to find where heat is being trapped. Some of these paved/built surfaces can reach up to 95 degrees Fahrenheit or more, such as black asphalt pavements in direct sunlight. However, some surfaces and places may be less hot than others due to different amounts of vegetation, building orientation, wind circulation, precipitation, material color, and much more.

Salt Lake City from 300 West to the Wasatch foothills – red and white show hot buildings and paved surfaces. Blue and green show cooler vegetation. Satellite image from NASA.”

Many U.S. cities have taken notice to this extreme heat and have implemented some cool solutions.  For example, urban tree canopies are planted all throughout the Phoenix, Arizona to provide shade for residents, which led to an overall “temperature reduction of 4.3°F when compared with a treeless neighborhood.”

Salt Lake City is taking action as well:

• Maintaining a robust urban forest and tree canopy to reduce temperatures.
• Building new municipal buildings with light-colored rooftops.
• Implementing a Sustainable Infrastructure Executive Order, which prioritizes natural systems to aid with stormwater runoff, reduce temperatures, and improve overall infrastructure function.
• Including a requirement that park strips and front yard landscaping include 33% vegetation.

How to Stay Cool

Sound urban planning is important, but it’s still hot outside.

It’s important to remember that extreme heat events and heat-related illnesses can affect everyone in Salt Lake City, but especially individuals without cooling systems in their homes, small children, the elderly, pregnant women, and people who work outside.

However, follow these various strategies to help you from overheating this summer:

• Visit a Salt Lake County “Cool Zone”(public libraries, community centers, etc.)
• Drink plenty of water periodically (even when you are not thirsty)
• Schedule outdoor activities during the early morning or in the evening
• Check on friends/family who live alone without a cooling system
• Act to reduce the urban heat around your home.

Now, we can all take steps in improving our health and work towards reducing our contributions to this urban heat island. See, learning about urban heat islands was no sweat!