Arctic airmass heading south, reaching Texas and even Florida, with some areas facing temperatures of up to 45 degrees below normal

While the UK is getting less cold this week in the run-up to Christmas, temperatures in the lower 48 states of the US will be taking a plunge. Over the course of the weekend, an Arctic airmass that was sitting over northern Canada, characterised by extremely low temperatures and strong high pressure, slid to the south across Alberta and Saskatchewan into eastern states of the Pacific north-west. Temperatures across these regions averaged about -23C at around midday on Sunday.

Through the week, this airmass will slowly spread southward across central states, with temperatures ranging from 10-30 degrees below average. Later in the week, the airmass will extend to the south, reaching Texas and even Florida, with some areas possibly reaching up to 45 degrees below normal. This cold airmass is likely to interact with an area of low pressure across the eastern half of the country towards the end of the week, threatening significant snowfall in states such as Minnesota, Wisconsin, Iowa and Illinois.