US hot weather forecast: Millions of Americans to be hit by freak mini-autumn heatwave

A cold front dragging a wintry band of snow and ice from the north will clear by mid-week to allow summer’s return for an almost 3,000-mile stretch of the US.

A high-pressure ‘anticyclone’ will build over the region through the coming days pulling warm air in from Mexico.

Jim Dale, social commentator and senior meteorologist for British Weather Services, said: “This heat is coming out of Mexico, and is tropical and sub-tropical in nature.

“Temperatures will rise across the central states and the mid-west through this week, and I would not be surprised to see higher than 70F in parts of the country.

“Warm air is coming out of the Gulf of Mexico and across Mexico itself, so there will be rising humidity and the risk of rainfall.”

Colder temperatures will be confined to the north, although the tropical blast will bring an end to the recent wintry snap, he added.

However, rising temperatures through the week will throw the atmosphere into instability sparking a risk of storms, he warned.

He said: “A wide region of high temperatures is always going to allow low-pressure systems to form in an unstable atmosphere.

“The high-pressure system is quite shallow, so not especially strong enough to stop the lows forming.

“So, with the warmer temperatures, there will be the risk of rainfall in parts of the region over the next week.”

The US is about to see temperatures ‘rollercoaster’ as the mercury rockets across central regions.

Chicago, Illinois could hit 60F (15.57C) with Billings, Montana at 63F (17.22C), Bismarck, North Dakota 58F (14.44C); Salt Lake city , Utah 66F (18.9C); Denver, Colorado 69F (20.56C); Oklahoma City, Oklahoma 65F (18.33C), Omaha, Nebraska 69 (20.56C) and St Louis, Missouri, at 66F (18.89C).

Swaths of the US will benefit from temperatures around 5 to 15F above average, according to The Weather Channel.

A spokeswoman said: “Millions of us will be above average as we go right through to the end of the week with 152 million people seeing above-average temperatures by Thursday.

“Tuesday the warmth will still be across the Rockies through the plains into the Midwest.

“62F is definitely not right weeks away from thanksgiving, and we are expecting temperature of 15 to 20 degrees above average as we head for Wednesday.”

Weather Channel meteorologist Ari Sarsalari added: “We are seeing some really big changes in temperature, some temperature swings, a temperature roller-coaster.

“There is a ridge of high pressure that is starting to build into the central part of the country.

“Look where these temperatures are going to be by the beginning of the week, these temperatures are way above average for this part of the country.