SOUTHERN ENGLAND — The Met Office issued an amber extreme heat warning for much of southern England and south-east Wales. Temperatures are expected to reach approximately 30C over the weekend in these areas, with a forecast peak of 34C on Monday and Tuesday; this peak could be exceeded in some locations.

The UK Health Security Agency issued an amber heat health alert on Thursday for London, the south-east, the south-west, and the east of England. The agency warned that high temperatures could increase deaths, particularly among individuals aged 65 and over or those with pre-existing health conditions. High temperatures may also lead to more water-related incidents, including cold-water shock and drowning.

Ross MacLeod, water safety manager for the Royal National Lifeboat Institution, said: "Cold water shock is a real danger, which we particularly want people to be aware of. The sea or open water may look inviting during hot weather, but it remains cold enough year-round to trigger cold water shock, which can cause uncontrollable gasping, increased heart rate, and can lead to panic and drowning very quickly." He advised individuals to enter water slowly to gradually acclimatise to the temperature. MacLeod added: "Anyone who finds themselves in danger in the water should fight the panic instinct and 'float to live': try to relax and float on their back, with head tilted back, gently moving their hands and legs to help them stay afloat. This buys valuable time to get your breathing back under control, before then calling for help or swimming to safety." He urged bystanders not to enter the water to rescue someone in distress, instead recommending they contact emergency services, instruct the person to float, and throw a buoyant object.

Greg Wolverson, a deputy chief forecaster for the Met Office, said: "While heatwave criteria will be met for some in the south and south-east of England over the weekend, with temperatures into the low 30s [C] possible, the warmth will expand and intensify at the start of next week, which, coupled with high temperatures overnight, leads to potential impacts. Tropical nights – where the temperature doesn't drop below 20C – are also likely for some."

Sally Petitt, head of horticulture at Cambridge University Botanic Garden, said: "Some of the garden's rare plants, such as ligularias, will flag in the heat no matter how much water they have access to. They're not desperate for a drink, they just don't like the heat." She added: "They don't die overnight, but they very quickly show signs they are in decline." Staff at Kew Gardens will water plants early each day and damp down nursery floors to maintain humidity levels.