A heatwave alert was issued by the Met Office on Monday, warning that temperatures would rise above 30C (86F) for at least two consecutive days and remain about 15C (59F) at night.
Public Health England urged Britons to do their best to stay out of the sun until the heatwave is over – especially between 11am and 3pm.
But Malcolm Bell, chief executive of Visit Cornwall, called the warning a “nanny state with the biggest capital N you could possibly print”.
He told the MailOnline: “It may be roasting in the big cities but down in the West Country there’s a lovely sea breeze on the coast which lasts for about five or six miles inland.
“So while the Met Office might say it’s going to be 86F (30C), it actually feels more like 75F (24C), which is a beautiful temperature for us Brits.”
Steve Jordan, of the Eastbourne Hospitality Association in East Sussex, said: “We’ve had long hot summers in the past and I don’t remember warnings telling us not to go out in the sunshine.”
Businesswoman Michelle Dewberry said: “Obviously most people cannot stay indoors [until Friday].
“I do think we need to take it seriously.
“I’ve had skin cancer because of the sun, and it is nice to be out and about in it and we do have to take precautions.”
Monday was the hottest day of the year so far, with 33.3C (91.9F) recorded 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.
The amber heatwave alert will be in place until Friday, when rain and thundery showers are forecast in parts of the UK.
The official guidance is to stay out of the sun and keep homes as cool as possible, shading windows and shutting them during the day.
This year has also been one of the driest on record, with many areas recording no more than 1mm of rain at once for 54 days.
The longest dry spell this year is Brooms Barn, near Bury St Edmunds, where there hasn’t been a drop of rain for 45 days.
Sky 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 (101.3F) recorded at Faversham in Kent on 3 August 2003? It’s too early to say.”
The hottest July day on record is 36.7C (98F), which was recorded at Heathrow on 1 July 2015.