The severe weather alert notification will come across every Echo device — in other words, whenever there is severe weather in area of your Echo devices’ associated address, the yellow ring will circle on all your Echo devices.
To enable severe weather alerts, just say “Alexa, tell me when there’s a severe weather alert.”
Once you enable severe weather alerts, the way you can double check that you’ll get a notification on all your devices is by opening the Alexa app > tapping the hamburger icon (horizontal three lines) in the upper left corner > tap “Settings” > tap “Notifications” > scroll down and tap “Severe Weather Alert in (name of where you live)” and under “Delivery” make sure it says “Notification on all devices.” If you prefer you can select “Announce out loud” and then select the device.