I was a little involved in the setting the new warning levels for weather in the UK introduced because people were confused with the old ones. now it looks as if the new system is not understood properly and is getting confused with other incident alerting systems.
WEATHER Alert Levels go:
Green, No Severe Weather
Yellow, Be Aware
Amber, Be Prepared
Red, Take Action
Red as a WEATHER alert is NOT a national emergency, I don't know where that has come from. Please read:
Weather Warning Levels There is another, different system used to inform health care and social services of the possible effects of long durations of COLD so hospital care may be prepared and provision made to look after the old and vulnerable. This involves a mix of temperature and duration to trigger the alerts which trigger the national 'Cold Weather Plan' responses.
UK Cold Weather Plan Although it is not restricted in any way it is not really for public use, just local government and emergency services.