Key to warning colours

Warnings are based on a combination of:

• Likelihood — How likely the event is to occur;
• Impact — The potential impact the expected conditions may have.

The combination of likelihood and impact is measured against a matrix to give each warning a colour:

• red;
• amber;
• yellow.

An example of the matrix used to define the warning colour is shown below. In this case, an event with a high likelihood and medium impact would result in an amber warning.

The matrix information showing how a warning was assigned its colour will be available for all warnings via the ‘View Warning Assessment’ option. However, you don't need to view this level of detail if you don't want to. You can simply use the following guidance for each colour:

For examples of the level of disruption that might be found at each of the impact levels and for each weather element (rain, snow etc.) see our severe weather advice page, which also includes information on what you may need to do.