On iPhones/iPads, audio alerts will not be audible if your phone is silenced, muted, on vibrate or "Do Not Disturb," however the push notifications will still be sent. This is how iOS devices are set by the manufacturer and we have no control over this. If not silenced, audio notification for the most pressing alert types will wake you up!
For Android devices (MWN app only), "wake-me-up" audio alerts (Severe Thunderstorm and Tornado Warnings) will override a user's vibrate/silent setting, however notifications for other weather alerts will not.
If severe weather is expected, especially overnight, it is best to leave your phone’s ringer or notification sounds turned on.