Heat-Health Watch

A Heat-Health Watch system operates in England and Wales from 1 June to 15 September each year in association with the Department of Health and the Welsh Assembly.

The Heat-Health Watch system comprises four levels of response based upon threshold maximum daytime and minimum night-time temperatures. These thresholds vary by region, but an average threshold temperature is 30 °C by day and 15 °C overnight.

Heatwave threshold values:

These temperatures could have significant effect on health if reached on at least two consecutive days and the intervening night.

Heat-Health Watch regions:

What do the different levels mean?

Green — Summer preparedness and long-term planning

This is the minimum state of vigilance during the summer. During this time social and healthcare services will ensure that all awareness and background preparedness work is ongoing.

Yellow — Alert and readiness

Triggered as soon as the risk is 60% or above for threshold temperatures being reached in one or more regions on at least two consecutive days and the intervening night. This is an important stage for social and healthcare services who will be working to ensure readiness and swift action to reduce harm from a potential heatwave.

Amber — Heatwave action

Triggered when the Met Office confirms threshold temperatures for one or more regions have been reached for one day and the following night, and the forecast for the next day is greater than 90% confidence that the day threshold will be met. This stage requires social and healthcare services to target specific actions at high-risk groups.

Red — Emergency

Reached when a heatwave is so severe and/or prolonged that its effects extend outside the health and social care system. At this level, illness and death may occur among the fit and healthy, and not just in high-risk groups.