The United Kingdom on Friday issued its first-ever red warning about exceptional heat as the typically mild country braces for triple-digit temperatures.

Officials announced the red warning, which constitutes a national emergency and means even healthy people are at risk of death, in anticipation of severely high temperatures Monday and Tuesday across central, northern, eastern and southeastern England, though weather will also be very hot in other regions of the U.K.

Here in the U.K., were used to treating hot spells as a chance to go and play in the sun, Penny Endersby, the chief executive of the U.K. Met Office, the countrys weather service, said in a video message . This is not that sort of weather. Our lifestyles and our infrastructure are not adapted to what is coming.