A week of extremes in the US as Arctic air plunges southwards across many states, sweeping away record-breaking warmth from last weekend. With low pressure in the west drawing up warm, humid air from the Gulf of Mexico, much of the south and midwest basked in spring-like weather this weekend with temperatures widely an extraordinary 15-20C above normal for late December.
This week, however, most people will ditch their summer clothes for hats and scarves as a ridge pressure builds across the west, allowing for a polar air mass to dive southward, bringing freezing temperatures and the risk of snow.
