By Jon King A fierce polar blast is poised to send temperatures in northern Britain diving down to -13C, recent weather maps reveal. In Argyll and Bute, on the west coast of Scotland, temperatures are set to plunge to -13C overnight on February 28. Parts of the Scottish Highlands could also reach lows of up to -11C. According to weather maps from WX Charts, temperatures could drop as low as -7C in northern parts of the Highlands on that same date. Elsewhere in Scotland and northern England, it’s also going to be chilly with temperatures expected to range between -1C to -5C. WX Charts’ maps rev…