Netro can work without wifi up to one month since Netro always keep one month schedule on local. So wifi only get most updated watering schedule to Netro from cloud, not control Netro open valves. If there is power outage when Netro is watering, it will shut off valves immediately. If there is no wifi when Netro is watering, Netro will still finish all watering schedules as long as there is power.
Netro will send notification when the system is offline more than 24 hours. But you need to enable Netro App notification in your smart phone settings.