The Met Office has forecast a significant temperature increase in the UK, with southern areas expected to reach 26C on Friday. Despite the anticipated warmth, western regions may experience showers, while eastern parts, especially in south-east England, will remain sunny and humid. The ECMWF weather model indicates that up to 38 counties will see temperatures hit 20C or above, with the highest readings expected around London and the Midlands. However, this warm spell will not be classified as an official heatwave, which requires temperatures to exceed the heatwave threshold for three consecutive days. The weekend is projected to bring unsettled weather, with scattered showers and potential thunderstorms in England and Wales. Monday will likely be cloudy with lingering rain in some areas, although sunny breaks may occur in the far south and north-west.