Toronto registered 13 degrees Celsius, (14C above average), New York City's Central Park had a reasonable 8C, and Washington, DC recorded a ridiculous 18C, (12C above normal). Given that last weekend it was about -10C with snow on the ground, this was a significant warming, and thaw.
After two weeks below freezing, the salt water Cape Cod Canal has a surface of chunky ice. Temperatures have regularly dropped below -15C at night in Massachusetts and Rhode Island since the end of last year. This is well below the freezing point of sea water, which is typically -2C. A coastguard boat was breaking ice in the Boston Harbour on Thursday.
The record-breaking Arctic freeze at the start of the year has frozen much of the Great Lakes’ surface. Rivers in the northeast flow with pancake ice on the surface; ice chunks are causing jams under bridges. The rapid thaw of snow with the falling of warm rain is now putting residents in New England under risk of flooding.
But the warmth and flood risk will be short-lived. Another wave of Arctic air is rapidly advancing from the Midwest.
Chicago had a warm 15C day on Thursday. Overnight the figure dropped to -5C, a temperature which was maintained on Friday. Saturday is likely to be no warmer than -8C.
The same thing happened in Toronto on Friday. In 18 hours, the temperature dropped 23 degrees Celsius, down to -12C, which was last seen less than a week ago. As this Arctic front marches eastwards again, winter weather warnings are in force from Kentucky to Maine.
Icy roads in Arkansas and Tennessee caused numerous vehicle collisions. Freezing rain in Pennsylvania and New York could bring down power lines, as well as slicken roads. Snow is expected to follow.
Snow was reported on Friday as far south as Louisiana.
Atlanta, Georgia felt the cold slap as well, as temperatures dropped from 14C to -2C.
Rochester, New York reported 10cm of snow overnight as the temperature fell from 15C to -7C.
Ultimately the rapid drop in temperature will be the most obvious change for the eastern parts of the US and Canada.
Sunday’s high, although in the sunshine, will be -9C in Toronto, -5C in Boston, -4C in New York City.