Smells.

Food science taught me that warm things smell more. The particles of scent vaporize at higher temperatures and waft into our nose and mouth, providing scent and what we know as flavor.

Another Southern California anomaly pertains to this. As I have switched to running in early morning or evening, or - by the Grace of Mercy - had the opportunity to run in cool weather, I've noticed more scent. The desert is sweet, peppered with sage and other spicier aromas that I cannot identify. I can smell the sweet dry grass and the vanilla aroma of temporary construction near sidewalks (see above). In the cool morning air, less pleasant scents like sewage and rotting fish waft from the water near the harbor or at Mission Bay. Without heat comes scent. I cannot find scientific justification for this.