Temperatures are set to climb further across the United Kingdom as the year's third heatwave spreads north and west, with highs of 35C (95F) expected on Thursday. The current heatwave, which began earlier this week, is notable for its duration rather than record-breaking temperatures.

On Wednesday, the mercury reached 33.8C at Heathrow Airport. Other parts of the UK also experienced significant heat, with Wales recording 31.2C in Cardiff, Scotland reaching 29.0C in Aboyne, and Northern Ireland seeing 27.1C at Helen's Bay.

The peak temperatures for this heatwave are anticipated on Thursday and Friday. High pressure across the country will maintain dry and settled conditions, allowing heat to build. While not expected to surpass the 37.7C recorded in June, maximum daily temperatures could reach 34C in London and Cambridgeshire, potentially hitting 35C in some areas.

By Friday, the high-pressure system is forecast to shift northward, extending the heat into parts of southern Wales and the Midlands, with temperatures in the low to mid-30s Celsius. A developing easterly breeze may bring slightly cooler conditions to eastern regions. Northern Ireland and Scotland are expected to experience mid-20s Celsius by Friday.

Amber heat health alerts are in effect for parts of the Midlands, eastern, and southern England until July 12, with yellow alerts covering northern England. These alerts indicate a significant likelihood of impacts on health and social care services, including an increase in mortality, particularly among the elderly and those with pre-existing health conditions.

The National Fire Chiefs Council has warned of an increased risk of wildfires due to the hot and dry weather. They have advised the public to avoid using disposable barbecues in open countryside, parks, and moorlands to mitigate this risk.

A heatwave is officially declared when specific temperature thresholds are met or exceeded for three consecutive days or more. These thresholds vary by region, with London requiring 28C, southeast England 27C, central England and southeast Wales 26C, and the rest of England, Wales, Northern Ireland, and Scotland needing 25C.

Parts of southern and eastern England have already met the criteria for an official heatwave, experiencing five consecutive days with temperatures above 30C. Other areas, including parts of the West Midlands and south, are also under official heatwave conditions.