I decided to walk around the neighborhood this morning because the weather has cooled down from over 100° during the day. I got dressed, put on my Monterrey sun hat (given to me by my beloved Mexican mother-in-law) to protect my bald head from the sun. It was 86° when I left the house, but the temperature recorded by my Garmin watch showed that it got up to 95° while I was walking with an average of 94.2°. That is still a good bit too hot for my Anglo/Finnish bloods so I think I will wait a couple of weeks before I try it again.
All that said, I have confirmed, again, my preference for walking around the neighborhood over walking on a treadmill. It is more fun (or at least, less boring), I walk faster and my heart-rate stays in the 50-85% optimal training zone for longer with less discomfort. I am not sure why that is, but that is they way it seems for me.