A heat warning has been issued for London as the longest heatwave of the year could begin in the coming days. A yellow heat health alert has been issued for parts of England as temperatures are forecast to soar to 31C on Thursday. The UK Health Security Agency alert will come into place at 10am on Wednesday and continue until 10am next Tuesday for the East Midlands, West Midlands, East of England, London, the South East and the South West. The Met Office said temperatures in some parts of the UK could surpass 30C – meeting the criteria for a heatwave – by the end of the week. Dan Holley, Chief Meteorologist at the Met Office, explained: "This heatwave is likely to last longer than previous ones so far this summer, and affect a wider area, with the focus for some of the highest temperatures displaced across more central and western areas at times." The Met Office has forecast constant sunshine for London until at least Monday, with temperatures consistently reaching 30C or higher. A heatwave is declared in London when there are at least three consecutive days where the daily maximum temperature reaches or exceeds 28C. Temperatures are expected to hit 28C on Wednesday while the Met Office has forecast the mercury will reach 31C on Thursday, Friday and Saturday, meaning the capital could be in a heatwave by the weekend. London saw the hottest day of the year last week when temperatures hit 34.7C in St James’s Park. It came as much of Europe faced hotter-than-usual temperatures, with a high of 40C recorded in Paris. Meanwhile, fire chiefs in London have warned a “rising tide” of wildfires is threatening to destroy public parks and wildlife. The London Fire Brigade has warned of the “devastating” impact wildfires could have on the capital’s green spaces and biodiversity amid extreme heat caused by global warming. Scientists have also claimed stifling heat is likely to become more frequent and severe in the coming decades. A total of £90,000 has been invested by the LFB and £40,000 by Labour mayor Sadiq Khan into wildfire management this summer, including the pilot of four specialist response vehicles.