After installing the RainAlarm chrome plugin, I discovered the iOS versions. Installed the free app first to try it out. Found it worked as advertised but a bit over-senstive. I purchased this version so I could change just how much rain would trigger an alarm. Like that I can switch the notification noise from the system default too. Something to keep in mind is that the alarm is only as good as the radar data. If there are "false-positives" from the Environment Canada (like noise generated by the Niagara Escarpment near Collingwood) youll be getting push notifications that rain is coming when its sunny out.
Gavia about Rain Alarm Pro Weather Radar, v1.7.1