On Christmas there was +20 degree C in a Iceland (this is 68 Fahrenheit)In Finland, much further south than entire Iceland, there was +2 degrees C (33 in Fahrenheit)https://www.kaleva.fi/itaisessa-islannissa-mitattiin-miltei-parikymmenta/12467781Expert said it it is due to "warm air mass had somehow concentrated on top of Iceland, it will go away in a few days"There is no sun there so sunshine is not the answer to the question.