I was truly shocked. I had a chat with AI about how much hotter it is on concrete, on blacktop, and on outdoor dirt paths. How much hotter is a blacktop parking lot surface than the “ambient air” temperature as reported.  I know that when I walk out of the supermarket or out of any air conditioned building, it is hotter in the parking lot. I know that when I walk across a blacktop parking lot it is a lot hotter than the ambient air temperature. But how much hotter? I was pretty sure that cement areas like sidewalks and to a greater extent cities with stone buildings and paved sidewalks and streets were at least 5 degrees F hotter than the air over grass.

I “knew” that over blacktop, the air was even hotter, perhaps another 5 degrees F. So if the air temperature is 95 degrees F, 35 degrees C, I thought parking lots/blacktop would be about 105, and cement areas generally about 110 degrees F, 38 degrees C because so much more mass was being heated than just the dark asphalt parking lots. I discussed it with AI. While not infallible, I have found AI to be generally right on. Even when the answer is hard to believe. Keep in mind that we are talking about the temperature of the blacktop, and not of the air above it.

Boy was I wrong about how hot parking lots really are. ! Here’s what AI has to say: Note that based upon what follows I am taking a break and turning the air conditioner to a lower setting!

Concrete and blacktop (asphalt) significantly increase temperatures in urban areas compared to natural landscapes like grass or trees. This phenomenon is part of what is known as the urban heat island (UHI) effect. Here are some specifics:

1. Concrete:
– Concrete absorbs and retains heat, leading to higher temperatures. During the day, concrete surfaces can be 10-20°F hotter than the ambient air temperature. That puts sidewalk areas, on Boulder’s recorded hottest day, 104 degrees F, 1at 114 to 124 degrees F. I believe the 114, and can’t imagine the 124 degrees F.
– At night, concrete releases the stored heat slowly, keeping the area warmer.

2. Blacktop (Asphalt):
– Asphalt is even more effective at absorbing heat due to its dark color. Asphalt surfaces can be 20-30°F hotter than the surrounding air temperature during the day. That puts it, where we walk, on Boulder’s historic hottest  104 degree day, at 134 degrees F to 144 degrees F. Can you cook an egg on a sidewalk? ABSOLUTELY! Over hard or hard scrambled would be easiest and fast! To not waste the overcooked egg, put the pan on the sidewalk and let it preheat for a few minutes. I would have demonstrated this for a photograph but it was too hot out today!

Do I really believe these numbers? NO I do NOT! A hot tub at 104 degrees F is really hot. An Idaho Springs soaking area at 112 to 114 degrees F, the hottest pool in the men’s baths, is unbearably hot. Granted the water heats a body very fast and quite thoroughly. But still! Wonder why people might break your car windows to let a dog or baby out on a hot day? A dog could cook faster in a hot car, windows open or not, than in a microwave! And so can you! Sorry for the graphic example, and it matters!

Lake Mead and Hoover Dam at about their lowest level. pic Lenny Lensworth Frieling

Is relief possible while walking in one of the amazing Boulder County Open Space areas? Happily, YES! Forget about shorts. Wear white, light-weight cotton from head to toe. Soak your hat. DO NOT WALK BAREFOOT!!! The right hat material might stay wet and cooling for an hour or more. I have experimented with this on my “Moses Trip.” I visited Las Vegas in mid-July during a heat wave. The temps were running 114 deg F in town, and a mere 110 at the Hoover Dam. Walking with a walking staff and dressed in white, with a soaked hat, it was almost tolerable. It did bring to mind images of Moses crossing a desert. I wanted to photograph Lake Mead at its lowest. Great photos!

I claim to be creative. I do not always claim to be very smart! My “Moses” trip was quite an event. One night I was sure I felt it cool down. My phone confirmed this, showing a drop to a mere 100 degrees F at 1:00 AM, in town, on a cement mall area near the Ferris wheel.

Comparison to Natural Surfaces
-Grass or Vegetated Areas:
– These surfaces tend to be cooler because they reflect more sunlight and through evapotranspiration (the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants).
Grass and vegetated areas can be 20-45°F cooler than nearby concrete or asphalt surfaces during peak sunlight hours.
Concrete: 10-20°F hotter than ambient air.
Blacktop: 20-30°F hotter than ambient air. On a 95 degree F day, that puts it around 120 degrees F while walking.
Grass/Vegitated Areas: 20-45°F cooler than nearby concrete/asphalt.

Keep in mind that these are NOT air temperatures, but surface temperatures. When bare feet are smoking under you, it is not your imagination. The parking lot or other surface might really be 120 degrees+ F.

The UHI effect can significantly impact energy consumption, health, and comfort in urban areas, making it essential to consider materials and landscaping in city planning.

I readily admit I was wrong. I was not a little bit wrong. I was WAY WRONG! Either that or AI is out of it’s artificial minds! I vote for the latter! So the next time you think it is hot out, consider that what you are walking on might not be a mere 104 degrees, but might be closer to 124 degrees F OR MORE!

Hot might just mean REALLY HOT!!! Think your feet are burning? THEY ARE!!!
Lenny Lensworth Frieling

Shared Knowledge Is Power!

Leonard Frieling Pen Of Justice

• Multi-published and syndicated blogger and author.
• University lectures at University. of Colorado, Boulder, Denver University Law School, Univ. of New Mexico, Las Vegas NM, and many other schools at all levels. Numerous lectures for the NORML Legal Committee
• Former Judge
• Media work, including episodes of Fox’s Power of Attorney, well in excess of many hundreds media interviews, appearances, articles, and podcasts, including co-hosting Time For Hemp for two years.
• Life Member, NORML Legal Committee, Distinguished Counsel Circle.
• Photographer of the Year, AboutBoulder 2023
• First Chair and Originator of the Colorado Bar Association’s Cannabis Law Committee, a National first.
• Previous Chair, Boulder Criminal Defense Bar (8 years)
• Twice chair Executive Counsel, Colorado Bar Association Criminal Law Section
• Life Member, Colorado Criminal Defense Bar
• Board Member Emeritus, Colorado NORML, and prior chair during legalization, as well as pre and post legalization
• Chair, Colorado NORML, 7 years including during the successful effort to legalize recreational pot in Colorado
• Senior Counsel Emeritus to the Boulder Law firm Dolan + Zimmerman LLP : (720)-610-0951
• Board member, Author, and Editor for Criminal Law Articles for the Colorado Lawyer, primary publication of the Colorado Bar Assoc. 7 Years, in addition to having 2 Colorado Lawyer cover photos, and numerous articles for the Colorado Lawyer monthly publication.
• http://www.Lfrieling.com