Four days in April
On 14 April 2003, on his way to skiing solo from Canada to the North Pole, Pen Hadow reported the temperature that day to be -26°C.
On 14 April 2004, during my solo North Pole expedition, the temperature was -19°C. (at an almost identical latitude).
On 14 April 2005, Tom Avery's Ultimate North dog sled team reported a daily temperature reading of -17°C.
On 14 April 2006, David de Rothschild's Adventure Ecology expedition (from 88 degrees North) noted it was -6°C.
I'll leave you to do the calculations.
— Filed under Climate Change, Other expeditions