The Iro actually stores all of your fixed schedules and will run as normal without internet connectivity. The only thing you won't benefit from is weather intelligence. (i.e. rain delay, water budgeting). Even if internet goes out, Iro is power cycled, it still has access to your fixed schedules.
For flex schedules and their dynamic nature, we store a backup copy of the flex schedule on the device and default it to a 2 or 3 day fixed schedule, just in case the Iro is disconnected for over a day, we will still water on a fixed schedule, just in case the internet has not come back for a couple of days.
Hope this helps.