Londoners looking to cool off from the hottest ever May day have access to 4,000 free water refill points across the capital.

Mayor of London Sir Sadiq Khan reminded overheating residents in the capital they can refill their water bottles across London.

How dangerous is dehydration?

One of the main risks of a heatwave is dehydration, along with overheating, heat exhaustion and heatstroke, according to the NHS.

Symptoms of dehydration can include: 

• Feeling thirsty
• Headache, feeling light-headed or dizzy
• Dark yellow, strong-smelling urine
• Urinating less often than usual
• Feeling tired
• Having a dry mouth, lips and tongue
• Sunken eyes

Warm overnight temperatures could bring restless night in south

Britons in the south could be in for another warm night, according to the Met Office.

The weather agency warned that the minimum temperature “usually occurs in the early hours, so it’ll be even warmer at bedtime”.

“This can make for a restless and uncomfortable night’s sleep, with little relief from the heat,” it added.

Our meteorologist Steff Gaulter said warm temperatures overnight can be dangerous because “it doesn’t give the body that respite it desperately needs”, posing a risk to vulnerable people.

Some of us are in for another warm night, particularly in the south 🥵

Remember, the minimum temperature usually occurs in the early hours so it’ll be even warmer at bedtime

This can make for a restless and uncomfortable night’s sleep, with little relief from the heat 😴 pic.twitter.com/LWnaMAMz5B

— Met Office (@metoffice) May 26, 2026