Air currents and long straight road surfaces heating up simultaneously as the sun moves.
Long straight roads in grids can cause the air to "stick" to the ground as wind moves overhead. And the sun hitting roofs and sides of buildings over shorter periods mean less "stored heat".
Some of it can be alleviated by having trees along the sidewalks. Since they help disperse wind and creates shade for the concrete/asphalt that store heat a lot longer.
EDIT: If you have more "random" road layouts with trees, there's less sun heating up the sidewalk and road. And the wind is more likely to be pushed around and prevent hot air from stagnating or circulating in an area.
Whether out in public or in private is better, depends on context.
Although it's probably a bit beyond social media debate. When it comes down to "seeing a strangers body floating in the river" , "finding your sibling hanging in the next room" or "found at a kindergarten playground".
spoiler
All of those examples are based on real life acquaintances who ended their lives, and their discovery. And to be clear: The kindergarten one was discovered before the kids arrived.