A rare red health warning is issued as a heatwave moves across parts of the UK, with forecasters warning that the extreme conditions may affect public health and transport. Sources report that the warning is unusual for the UK, reflecting the severity and rarity of the heat at this level. Alongside high temperatures, the conditions include high humidity, which can increase the risk of heat-related illness, particularly for vulnerable groups such as older people, those with underlying health conditions, and outdoor workers. Forecasters also highlight very warm nights, meaning temperatures do not fall significantly after dark, which can make it harder for people to cool down and recover. Transport operators and local services are expected to face challenges during the hottest periods, with heat able to disrupt travel and infrastructure performance. The warning advises attention to heat safety measures, with guidance focused on reducing exposure and taking precautions to stay hydrated and cool. The alert remains linked to forecasts for the timing and duration of the extreme weather, with monitoring continuing as conditions develop.