Yorkshire is braced for a “Spanish Plume” weather event this weekend which could cause severe storms, flash flooding and even tornadoes.
Hot and humid air is expected to be pushed into northern Europe, creating the phenomenon, forecasters said.
It comes after US scientists found that July was the warmest month on record worldwide and 2015 is likely to be the hottest year.
As the wind becomes southerly on Friday and Saturday, a brief surge of heat from the continent will affect central and eastern parts of England.
The heat and humidity in central and eastern areas could trigger severe thunderstorms, especially for the Midlands and northern England. Hail and strong wind gusts are possible.
Heavy rain is likely to become widespread through the weekend, especially in the west and north. Severe thunderstorms may affect some areas, MeteoGroup said.
Yorkshire is likely to escape the most severe weather, but should prepare for a soaking.
MeteoGroup forecaster Matt Martin told The Yorkshire Post: “Today we have a weak cold front starting across the west of Britain. This will remain almost stationary through the day with some outbreaks of rain in the Yorkshire region, becoming more persistent over night.
“Tomorrow it will move further west and through the late afternoon and evening there is a threat of some thunder storms breaking out in the region. Between 6pm and midnight tomorrow is the period with the highest risk of thundery downpours.
“It’s going to be quite muggy tomorrow with temperatures around 24 or 25 degrees and staying warm overnight.
“On Sunday the rain will push back westwards, so it will become dry late morning, but the risk of rain will return in the evening and overnight.
“We can’t be too specific with these plumes. They happen two or three times a year and can result in some extreme outcomes.”
The weather is likely to vary across the region, with the coast seeing the better weather tomorrow, with “some sunshine across the eastern region, Mr Martin said.
He said: “During the afternoon it could be dry towards Scarborough with periods of hot sunshine but there is still a risk of thunderstorms tomorrow evening and overnight, but it certainly has more chance of drier weather.”
The regions most likely to see fairly hot weather include London, which could see temperatures of around 30C (86F) on Saturday, Norwich and Cambridge at 28C (82.4F), and Bath, Birmingham and Lincoln at 25C (77F) or 26C (78.8F).
However, it looks like a slow-moving frontal system will affect western parts of Britain, with heavy rain developing through the course of Saturday.
The rain and areas of thunderstorms then look like spreading into Scotland overnight and into Sunday, with further rain or showers still possible further south. Northern Ireland may escape much of this activity. The unsettled conditions could last into the start of next week, before turning cooler again.
Officials at the National Oceanic and Atmospheric Administration in Washington DC said July’s average global temperature was 16.5C (61.86F), beating a previous record set in 1998 and 2010.
The first seven months of this year were the hottest January-to-July span on record.
:: A Spanish Plume is a colloquial description of a weather situation in which a large southwards dip in the high altitude jet stream develops to the west of Europe, encouraging a deep southerly wind flow. This pushes hot and humid air from Iberia north and north-east into northern Europe, including the British Isles.
The proximity of active weather systems moving with the jet stream along with heat from the summer sunshine can encourage thunderstorms. The strong winds from the jet stream help to organise the thunderstorms and can increase their severity.
Forecasters said the Spanish Plume can create a risk of tornadoes, although there is a low risk of that this weekend.
With the final days of the summer holiday and a bank holiday weekend approaching, Mr Martin said we can expect unsettled weather next week, with temperatures coming back down to the average for this time of year, with a mixture of showers and longer spells of rain.
There are some signs of high pressure which could mean a good bank holiday weekend, and it will “more than likely” be more settled, he added.