Monday was the hottest day of the year so far as temperatures have peaked at 33.3C (91.9F) in Santon Downham, Suffolk.
It could get hotter, as the Met Office warns of temperatures peaking on Thursday and Friday - potentially hitting the mid 30s.
It comes as it issued an amber heatwave alert, warning Britons to stay out of the sun between now and Friday.
The warning is in place until 9am on Friday for parts of England as scorching temperatures are expected to continue.
Official guidance is to stay out of the sun and keep homes as cool as possible, shading windows and shutting them during the day.
The amber, or level three, warning is issued when temperatures are predicted to hit 30C (86F) during the day, and 15C (59F) at night for at least two consecutive days.
The Met Office forecasts "very hot" weather in east and southeastern areas, with long spells of sunshine ranging from "very warm" to "hot and humid" in the West and East Midlands.
Matthew Lewis, deputy chief meteorologist, said: "The heatwave conditions will continue for much of England through this week, with temperatures possibly into the mid 30s in places on Thursday and Friday."
The balmy conditions could continue well into August, staying mostly hot for the rest of the month.
Sky's weather producer Chris England says: "It's quite a long time to August in weather forecasting terms, but it doesn't look like things are going to change that much from the last few weeks.
"Will we beat the UK record temperature of 38.5C recorded at Faversham in Kent on 3 August 2003? It's too early to say."
The heatwave has also gripped much of Europe, with extreme heat affecting farmers in Poland, Sweden and Finland.
Sweden is seeing its hottest summer for a century, and temperatures in Finland have comfortably outstripped their typical highs of 18C (64.4F), reaching 30C in places.
Britons are advised to take precautions during the heatwave, including staying out of the sun during the hottest times (11am to 3pm), wearing sunscreen and staying hydrated.
The temperatures on Monday beat the 33C (91.4F) recorded in Porthmadog in Wales on 28 June.