UK weather forecasters are predicting the best summer in a century this week, with temperatures of at least 30C lasting from the start of June until the end of August. Some models are even suggesting that we may soon see the British record for the highest ever temperature – 38.5C (101F) – beaten this year.

Forecasters believe we will experience an unusually intense heat surge which should travel from Europe at the start of next month and kick off a series of heatwaves. They are blaming a rare meteorological convergence, during which the jet stream will veer suddenly northwards, bringing with it much hotter air from Africa and Europe.

The jet stream's unexpected swing is a result of an El Niño effect – a formation of extreme weather in the Pacific – which is gathering with particularly unusual force this year. As well as being blamed for the unusual number of Atlantic storms that have recently battered the UK, it caused a massive change in ocean temperatures in 2015.

The El Niño is expected to be followed by a rarer La Niña event, which will cause an equally sudden drop in temperature.

This variation in water temperature will cause a massive knock-on effect on both atmospheric temperatures and on global climate patterns. And because both El Niño and La Niña are set to be especially strong, the resulting weather patterns will be similarly extreme.

These events will change the flow of air between the warmer tropics and mid-latitude regions, such as the UK, which rarely experience such wild extremes of temperature. In a final stroke of happenstance, the peak of the entire pattern looks to be coming just as Britain enters the summer months.

UK Hot Weather
An El Niño effect will give the UK its hottest summer in 40 years Mike Hewitt/Getty Images

Rebecca Lindsay, of the National Oceanic and Atmospheric Association (NOAA) said: "This shift disrupts the atmospheric circulation patterns that connect the tropics with the middle latitudes, which in turn modifies the mid-latitude jet streams. This can affect temperature and precipitation across the world."