Temperatures are forecast to reach as high as 29C (84F) in parts of Northumberland today.
Parts of central and southern England could reach 35C (95F) on what is expected to be the hottest day of the year.
In Northumberland, temperatures are forecast to reach 29C in Hexham, 24C in Morpeth, 23C in Alnwick, 22C in Berwick and 21C in Blyth.
However, it will not last.
The Met Office has issued a weather warning for later today.
It has issued a Yellow Alert of Rain for North East England valid from 5pm today until 6pm tomorrow.