Thanks for the reply!
Right, but the signal from the rain sensor doesn't cause any added water calculation, right? For a fixed schedule, it sorta does (I know there's not actually any calculation needed in that case, but it can reduce the water to the lawn by skipping watering).
That's what happens for a Fixed schedule: the watering is skipped. For a Flex schedule, the watering is delayed until after the sensor deactivates, right?
What I'm saying is, with a Fixed schedule, the rain sensor can make your lawn be watered less (less total water volume). For a Flex schedule, the rain sensor cannot reduce overall water usage, it would only push watering to a later date.
It might help to imagine that the weather station you're looking at is broken and not reporting any rain. The rain sensor can help the Fixed schedule save water, but not the Flex schedule.
So I'm just trying to think if there is any reason to use a rain sensor if you use only Flex schedules.