How cool are your trees?

How do trees cool?

• Trees and other vegetation shade the ground, reducing the radiation absorbed from the sun.
• Without trees, the ground surface heats up from radiation absorbed by pavement and buildings.
• The evaporation of water from soil and leaves (evapotranspiration) also cools the air.

What is the “urban heat island?”

• “Urban heat islands” form as vegetation and natural areas are replaced by asphalt and concrete for roads, buildings, and other structures.
• These surfaces absorb—rather than reflect—the sun’s heat, causing surface temperatures and air temperatures to rise.
• Many cities have air temperatures up to 10°F warmer than the surrounding natural areas.
• Temperatures decrease at night, after the sun sets. But cities still stay warm because there is heat stored in the roads, buildings and other structures.

How hot or cool is it?

• Buy or borrow an infrared thermometer. Point the thermometer directly at unshaded ground surfaces, such as concrete, asphalt, grass, or dirt.  Then do the same for similar surfaces that are shaded by a tree.   What is the difference?  According to the EPA you can see temperatures of surfaces shaded by trees be up to 45-degrees cooler than surfaces in direct sunlight.