It's one level below a national emergency
The Met Office has issued an amber heatwave warning for Devon and Cornwall this week.
The spell of hot weather is expected to last from Thursday until Sunday.
The Met Office say: "The alert level has increased for Southwest England, as confidence in hot weather and warm nights affecting at least the far east of the region has now increased.
"The alert level in all other regions remains unchanged. Hot or very hot conditions are likely across southern, central, and eastern parts of England from Friday as warm air spreads north from France."
"These conditions are likely to persist into the weekend, perhaps being eroded from the northwest by less hot and cloudier conditions for a time, with the slight releiving conditions currently probably reaching a southern limit over central parts of England."
The Met Office advise people to look out for others, especially older people, young children and babies and those with underlying health conditions.