01/20/2026
Big Fat Deal here...
https://www.facebook.com/story.php?story_fbid=1475270921271933&id=100063671171571&post_id=100063671171571_1475270921271933&mibextid=NOb6eG
I found myself explaining the Urban Heat Island to a Cop a few days ago, after I had the cops called on me (for the second time) while planting street trees on public property. When he asked me why I was planting trees (but didn't tell me I couldn't do it), my reply was first and foremost "shade". As I explained what "thermal inertia" was and how concrete and asphalt had a *high thermal inertia* (or thermal mass), his eyes wandered like a bored highschool student and his interest faded off like a fart in the wind.
Though the cop wasn't interested, maybe you are, and maybe you can use this info to help convince your city and county to plant more street trees. Street trees are not a "Feel good" symbol, and I'm not planting them for "beautification"...they are an essential piece of URBAN INFRASTRUCTURE and help mitigate both the urban heat island and - along with native shrubs - help reduce the potential for flooding. I'll post a synopsis here:
THE URBAN HEAT ISLAND EXPLAINED:
If you go out with a laser thermometer and measure the temperature of the surface of a parking lot in South Texas just before sundown, it'll be around 141° F.
For a 6-inch thick asphalt slab starting at 141°F (60.6°C) on a calm, clear summer night with a low of 75°F (24°C), it would take approximately 12-14 hours for the surface to cool to within about 10°F of the ambient air temperature.
Asphalt doesn't cool like a cup of coffee. It's a solid slab losing heat from its surface. The interior heat must conduct to the surface before it can radiate away. This internal resistance is why cooling is slow.
This long cooling time reveals the severity of the problem:
The Night is Not Long Enough: With only ~10-12 hours of darkness in summer, the asphalt never reaches equilibrium with the night air. It's still actively radiating significant heat at sunrise.
Cumulative Heat Build-Up: On multi-day heat waves, each day starts with the pavement already pre-heated from the previous night, leading to even higher peak temperatures.
The "Space Heater" Metaphor : This 12-14 hour cooling time means the asphalt is indeed a vast, low-temperature radiator from sunset until just before dawn, directly causing the elevated nighttime urban temperatures.
Every new parking lot, road, and stretch of asphalt that is not somehow blocked from the sun, whether by trees or by sheet metal pergola structures and carports, must be seen for what it is : a layer of material that will effectively become a night-time space heater during the summer.
