Key to warning colours

Colour and risk levels for severe weather events (can often occur, particularly in winter)
 
Green
Yellow
Amber
Warning
None
Advisory
Early
Flash
Risk

Very low
<20%

Low
≥20% <40%

Moderate
≥40% <60%

High
≥60% <80%

 Very high
>80%
Headline No severe weather expected Moderate risk of severe weather High risk of severe weather Severe weather is imminent or is occurring
Impact     Moderate risk of some damage to infrastructure and local disruption High risk that there will be some damage to infrastructure and local disruption Very high risk that there will be some damage to infrastructure and local disruption
Advice     Ensure you access the latest weather forecast Remain vigilant and ensure you access the latest weather forecast Ensure you access the latest weather forecast and take precautions where possible

Colour and risk levels for extreme weather events (these are rare)
 
Green
Yellow
Amber
Red
Warning
None
Advisory
Advisory
Early
Flash
Risk

Very low
<20%

Low
≥20% <40%

Moderate
≥40% <60%

High
≥60% <80%

 Very high
>80%
Headline No extreme weather expected Low risk of extreme weather Moderate risk of extreme weather High risk of extreme weather Extreme weather is imminent or occurring
Impact   Low risk of major damage to infrastructure and the environment Moderate risk of major damage to infrastructure and the environment High risk of major damage to infrastructure and the environment. Casualties are possible Major damage to infrastructure and the environment is likely. Casualties are possible
Advice   Ensure you access the latest weather forecast Remain vigilant and ensure you access the latest weather forecast Remain extra vigilant and access the latest weather forecast. Be aware of risks that might be unavoidable. Follow any advice given by authorities Remain extra vigilant and access the latest weather forecast. Follow orders and any advice given by authorities under all circumstances and be prepared for extraordinary measures
UK warnings key to colours

As a quick guide to the colours, they should be interpreted as:

'Be aware' means: Remain alert and ensure you access the latest weather forecast.

'Be prepared' means: Remain vigilant and ensure you access the latest weather forecast. Take precautions where possible.

'Take action' means: Remain extra vigilant and ensure you access the latest weather forecast. Follow orders and any advice given by authorities under all circumstances and be prepared for extraordinary measures.
What to do before, during and after an event (see links)
Severe gales Heavy rain Heavy snow and icy roads Thunderstorms and lightning Heat and sun Dense fog
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