There are three options for rain delays 1) Full Automatic, the server sets them for you 2) Suggested, the server will only suggest that you set a delay yourself 3) Disable the Notification, you can turn off Smart and Notifications for delays and you won’t get any.
If you have Smart Watering enabled for the system the server will automatically set rain delays for you. You can control these thresholds in the Device Detail screen under Weather Adjustments so that it’s more or less sensitive to the forecast and amount forecast.
If you have Smart Watering disabled but you still want to know when you might want to set a delay you can enable the rain delay notifications and you will get suggested rain delays only.
If you turn them all off then it’s completely up to you when you want to turn them on or not.
Hope this helps!