The impacts of heat on population health can be divided into three categories, the likelihood of which would be indicated by the issuing by Met Éireann of a high temperature (yellow / orange / red) warning. In addition, there may be regional, urban/rural or other variations across the country in relation to the severity of a heatwave. Accordingly, the following should be used as a general guide, and there may be instances where public health effects of heat may arise outside the classification applied by Met Éireann. Nonetheless, the following categorisation is intended as a guide to inform the type of advice and action which may be appropriate.