Great information here!
We shoot in SoCal and while the temperature swings aren't quite as dramatic as some in this thread, we too have discovered that there are POI differences when shooting in the morning at around 70° until noon time which at times is mid 90°-100° at times. Shooting of my truck hood gets extremely hot as well, reflecting heat. It's very common to readjust our scopes a few times to accommodate these temperature swings. For the most part though, we were thinking that the POI shifts were mostly due to the heating of the metals, the shroud being black and absorbing heat first shifting the barrel within (Crowns and Impacts). So, it's our belief that while temperature affects the pellet, it also indicates that it affects the surface and then the internals of the rifle itself as it heats up throughout the day.
No?
mike