For where the data is from -
Tessie: Awesome software for your Tesla - It's fairly slick for data collection, I'm a big fan of it so far. No other 3rd party apps.
Scheduled Departure - Not turned on. We haven't used that feature as we don't have a regular schedule these days, but I double checked - still off.
Cabin Protection - Yes, that is turned on, but Tessie indicates when that is active. It also doesn't kick in until the cabin is over 100F. So this isn't related to that. The darker blue is when Tessie doesn't have up-to-date data due the vehicle being asleep. Example screenshot from a few days ago:
I had the car plugged in overnight charging, and noticed a similar trend.
Again, this was overnight, in a garage. The internal temperature "jumps" every 2 hours. Now it's also clear the "outside" (garage) jumps every 1 to 2 hours as well. At the exact same times. Now, as someone all about data, I also happen to have a temp sensor in the garage near the Tesla.
So the Tesla "outside" temp increasing overnight doesn't match up with reality (though it is within about 5F or so). I think the Tesla's sensor is probably affected by the fact that it was charging.
Overall, My theory is that the temperature "jumps" is due to idle sensors. When the car isn't driving I think even though the car is "awake" for either charging or sentry mode, not all of the sensors are. So the temp is either only polled every hour, or the data is only sent back to the mothership every hour. Which would make sense from a "reducing useless data" perspective. If the car isn't in motion and something like overheat protection isn't active, why bother updating the data frequently? It's a car, not a weather station.