I’m looking over the 2.5 release documentation and I’m unhappy with quite a bit of it. I’ll post about each topic once I’ve researched it enough to make sure I’m not prematurely judging it. However, I’m virtually certain your “Seasonal Shift” feature is just bad practice.
The “Seasonal Shift” feature is an improper technique for watering grass (at least in Florida). To quote UF (https://edis.ifas.ufl.edu/lh025), “The amount of water applied each time you irrigate your lawn should not vary seasonally, though the frequency with which you water will change by season.”
An explanation in my own words…
Constant water volume with variable frequency encourages deep root growth and thus a drought tolerant turf. Suppose roots can reach as much as 12 inches below the surface, every time you irrigate you should put down enough water to also reach a depth of 12 inches (NOTE, this doesn’t mean you apply 12 inches of water…UF recommends 1/2 to 3/4 inch). Then you wait until your lawn shows signs of drought and you repeat the process.
This works because when grass experiences (short-lived) drought it will respond by growing deeper roots as long as there is water to be found at the lower depth. So by only watering after signs of drought are visible and by always watering as deep as roots have the ability to grow, you are creating a positive feedback loop that promotes the deepest roots possible.
If your grass already has deep roots and you no longer water to that depth (perhaps because of “Seasonal Shift”) then you’ve created a “use it or lose it” scenario. The grass isn’t going to spend the energy maintaining deep roots if there is no water to be found at that depth. Similarly, if your grass doesn’t yet have deep roots and you’re not watering deep then it “knows” there isn’t any water to be found and doesn’t divert energy to growing deep roots.
I’m guessing the Rachio team intuitively thought “colder weather requires less water” then mistakenly applied that logic to the amount of water per application rather than (or perhaps in conjunction with) less frequent applications. Easy mistake to make but I don’t think it is right.