Arctic air has descended across much of the U.S., including Florida.

Holiday-makers who have travelled to Florida for a bit of winter sun would have been given a shivery shock this morning waking up to temperatures of 2C (36F) in Tampa, and 3C (37F) at Fort Myers. In the state temperatures usually range between around 10C (50F) and 23C (73F) by day and night in January.

Temperatures have plunged across many parts of Canada as well, with the city of Toronto starting off with the mercury around -15C (5F) on Tuesday morning. In the Canadian capital it was even colder with temperatures here at -24C (-11F) to start the day, about 10 degrees below average.

In New York it was around -7C (19F) to start the day, while further south in Washington D.C temperatures fell to -9C (16F).

In the usually sultry Savannah, Georgia dropped to -1C (30F) on Tuesday morning. And in Havana, Cuba the mercury dipped to 10C (50F), quite a bit below its 17C (63F) average minima.

The cold plunge of air has been brought about by the jet stream moving a lot further south than usual. A jet stream, in simple terms, is a fast moving ribbon of air in the atmosphere that steers areas of low pressure and also marks a boundary between cold and warm air. The cold air lies to the north of it and the warmer air to the south.

Later in the week an area of low pressure that is currently crossing the south of the states could be intensified and whipped up the east coast by the jet stream. There is the potential that it will bring significant snowfall for the northeast on Friday and also for the Appalachian Mountains.

If you're off to Florida soon though then don't worry about taking the scarf as the weather should turn warmer again, with temperatures only falling to 19C on Thursday night in Tampa - what a contrast!