People walk along the bridge in St. James's Park in London, Britain, on July 20, 2021. Britain's national weather service the Met Office has issued its extreme heat weather warning as sweltering conditions have continued for several days in parts of the country. Issued Monday afternoon, the amber warning will last until mid-night Thursday with temperatures expected to drop on Friday. (Photos: Xinhua)

A woman poses for a photo in Green Park in London, Britain, on July 20, 2021. Britain's national weather service the Met Office has issued its extreme heat weather warning as sweltering conditions have continued for several days in parts of the country. Issued Monday afternoon, the amber warning will last until mid-night Thursday with temperatures expected to drop on Friday.

A gardener trims flowers in the scorching sun in front of Buckingham Palace in London, Britain, on July 20, 2021. Britain's national weather service the Met Office has issued its extreme heat weather warning as sweltering conditions have continued for several days in parts of the country. Issued Monday afternoon, the amber warning will last until mid-night Thursday with temperatures expected to drop on Friday.

Two girls walk in Green Park in London, Britain, on July 20, 2021. Britain's national weather service the Met Office has issued its extreme heat weather warning as sweltering conditions have continued for several days in parts of the country. Issued Monday afternoon, the amber warning will last until mid-night Thursday with temperatures expected to drop on Friday.

Waterfowl swim in a lake in St. James's Park in London, Britain, on July 20, 2021. Britain's national weather service the Met Office has issued its extreme heat weather warning as sweltering conditions have continued for several days in parts of the country. Issued Monday afternoon, the amber warning will last until mid-night Thursday with temperatures expected to drop on Friday.

People and vehicles pass by Buckingham Palace in London, Britain, on July 20, 2021. Britain's national weather service the Met Office has issued its extreme heat weather warning as sweltering conditions have continued for several days in parts of the country. Issued Monday afternoon, the amber warning will last until mid-night Thursday with temperatures expected to drop on Friday.