Temperatures could soar to 35C in parts of south-east England on Wednesday, with weather maps showing up to 20 counties facing 30C or above.
Temperatures to Peak on Wednesday
Tuesday will bring increasingly hot conditions, particularly across south-east England, where temperatures are forecast to climb to 29C or 30C, before reaching a peak on Wednesday.
A Met Office forecast map for 4pm on Wednesday shows highs of 34C in Cambridge and parts of Norfolk and Suffolk, along with 33C in London and parts of the Home Counties.
The soaring temperatures are expected to push conditions beyond the threshold needed to make it the UK's fourth heatwave of the year.
Heat Health Alerts Issued
Amber heat health alerts have been issued by the UK Health Security Agency (UKHSA) for the South East, the East Midlands, East of England and London. Yellow heat health alerts have been issued for the South West, West Midlands and Yorkshire and the Humber.
The alerts will be in place from 9am on Wednesday, July 29, until 9am on Thursday, July 30. As yet, there are no alerts in place for the North East or North West of England, Wales, Scotland or Northern Ireland.
The Met Office has said that, if temperatures rise high enough to meet local thresholds for three consecutive days, another heatwave could be recorded. So far, 2026 has seen three defined heatwaves, in May, June and July.
Counties Set for 30C on Wednesday
The following counties are forecast to reach 30C or above: Bedfordshire, Berkshire, Buckinghamshire, Cambridgeshire, Essex, Greater London, Hampshire, Hertfordshire, Kent, Leicestershire, Lincolnshire, Norfolk, Northamptonshire, Oxfordshire, Rutland, Suffolk, Surrey, Warwickshire, Wiltshire, Worcestershire.
Gregory Wolverson, deputy chief forecaster at the Met Office, said: "This is a short-lived spell of heat, but temperatures will climb quickly through the first half of the week, particularly in the southeast.
"By Wednesday, some areas could see temperatures in the mid-30s, and while the heat will not be widespread across the whole of the UK, it will be enough for parts of the southeast to likely meet official heatwave criteria by Thursday.
"Elsewhere, the weather will be more changeable, and the change to cooler, more unsettled conditions will arrive sooner from the north and west, with a mix of sunshine and showers. Across northern areas, it is possible there will be heavier showers with a small risk of isolated thunderstorms through the week."
