Although the mercury could reach its highest point so far yet this year in the ITV Meridian region, forecasters said the heat will be accompanied by high humidity and heavy, thundery showers
Temperatures will start to rise from Thursday, peaking on Friday when the 30C barrier could be reached for the first time this year, with the most likely location somewhere to the north-west of London.
Forecasts suggest the South coast will be slightly warmer than European holiday destinations such as Barcelona, Ibiza and Nice.
The hottest day so far in 2014 was July 4, when 28.7C (83.7F) was detected in Norfolk and Essex.
– Simon Parkin, ITV News Meridian weather presenter
Not great news for the superstitious is that there is a chance of patchy rain for St Swithun's Day tomorrow, which, according to the legend of the saint buried at Winchester Cathedral, we could have 40 days of very damp weather.