What are twitter alerts?
Twitter Alerts are Tweets published by select public agencies and emergency organizations during a crisis or emergency that contain up-to-date information relevant to an unfolding event, such as public safety warnings and evacuation instructions.
Alerts will appear highlighted on your home timeline and are instantly sent to your device as a mobile notification.
Where do I sign up?
For Boston - https://twitter.com/notifyboston/alerts
For Massachusetts sign up here - https://twitter.com/MassEMA/alerts
Everywhere else go to - https://about.twitter.com/products/alerts/participating-organizations