I have a 16 zone Rachio for three years. It has worked well. We are experiencing a wetter than usually spring and summer in central Texas. I turned on seasonal adjustment on July 2 2024 and walked away. Little did I know what would happen, and yes, I didn’t check anything. I received a bill today for using 29k gallons of water in a month. The seasonal adjustment changed my zone times from ± 20 minutes to between 52 and 90 minutes. On July 3, my watering day, the controller watered for 12 hours. And then it added more watering July 4th, not my watering day. I called the city to ask the to check the meter. Then I thought to check the Rachio history. Big mistake on my part to trust the controller to actually water less. I learned seasonal adjustment is not Smart. It presume the algorithm just applies extra water because it is summer. Not the case. I suggest a notification be made to let me know the change in water zone times. Waste of water and money.
Sounds like you are on Flex Monthly schedules? They are really just a fancy fixed schedule with some seasonal shifting and weather intelligence. Not really sure what you were expecting. If you want something to dynamically adjust to the wetter spring and summer, dial your settings in and run Flex Daily. They are a fully dynamic, always adjusting schedule that will account for daily changes in weather, rather than a 30 year aggregate of weather patterns found in the Flex Monthly.
Seasonal adjustment is smart…it just uses historical data to adjust, not real time.
I’m going to switch my devices from Flex Monthly to Daily and the explanation from @tmcgahey just confirms my hunch about how it works. Historic weather patterns are a pretty poor proxy with the heat waves and all the climate change. Unfortunately for some reason that I don’t understand it looks like you have to delete and create a new schedule and you can’t just toggle a button in the app. That seems like an easy thing to fix in the software.
Not entirely sure, but I believe the switching is not a thing because the two types have fields in the UI they do not share and since there was a wizard-like guidance to create a schedule, switching its type might leave things not initialized 
Just an educated guess.
Let’s Go!
Here to help if you need to dial settings in for a successful Flex Daily transition!
I tried again and, well, I just gave up on Flex Daily and Flex Monthly for my citrus tree because it kept skipping one or two days, thinking the soil was saturated. This is the desert and my citrus tree has rocks on a slope, so water retention is very low.
There are situations in the extremes of the desert where some kinds of plants must get at least a minimal amount of water every day and none of the 3 types of settings give me enough control over this. To add to this, all weather forecasts (not just Rachio) are not accurate here in terms of rain so often it can dump rain but a rain skip is not triggered.