News

Oregonian: Portland weather hot spots: Temperatures can vary as much as 20 degrees by neighborhood
Author: By Kale Williams, The Oregonian/OregonLive
Posted: August 29, 2018

Read the original story in the Oregonian. 

It's no secret that Portland has been on a hot streak, notching day after day of temperatures well into the 90s. It's been hot enough that the city broke its own record of the number of 90-degree days in a year. While Tuesday isn't expected to add to that tally, with an expected high in the upper 80s, it's still warm enough to feel like the height of summer.

But depending on where you are in the city, it might not feel that way. On a hot day, there are wild swings in temperature between Portland's microclimates, sometimes by as much as 20 degrees within just a mile or two.

That's according to Vivek Shandas, a professor at Portland State University's Institute for Sustainable Solutions, who lead the research team looking into the varying temperatures in the city. The research was first reported by the Portland Tribune.

Though the data itself was massive, with more than 300,000 measurements, collecting it was as simple as driving around Portland at predetermined times with a fancy thermometer sticking out the window.

The conclusions Shandas was able to draw from the research went beyond where the heat collects in the city. Shandas was able to discern not just where the hotspots were, but also why some places were so much warmer.

As with many ways the city works (or doesn't work), it all comes down to planning, Shandas said.

Different surfaces react differently to heat. Concrete, asphalt and other aspects of what Shandas calls "the built environment" absorb heat and warm their surroundings. But how the built environment is designed has an impact as well.

When buildings are all the same height, the air in between them can stagnate and bump temperatures up. Buildings of varying heights increase circulation and act like a breeze-driven air conditioner.

Nature plays a big role, too, Shandas said. Bigger trees absorb more heat from the sun and create bigger shadows. Plants pull moisture from the ground, which in turn evaporates into the air providing a cooling effect.

Some of the hottest places in Portland occur where those two dynamics -- the built environment and the natural one -- intersect. Buildings that are designed in a horseshoe shape, with a parking lot in the middle absent of greenery, can raise the temperature of adjacent buildings by as much as 10 degrees, Shandas said.

"There are numerous designs that could be far more effective" at reducing heat, he said.

Changing the planning and development process is no short endeavor, though, and those looking for relief from the increasingly hot weather likely don't want to wait for more efficient buildings to be constructed.

In the meantime, Shandas used his data to pull out some of the hottest places to avoid during a heatwave and a few more to head toward if you're looking to cool down.