As a photographer, I'm debating visiting Iceland in mid-March v. mid-April with the hope of seeing the Northern Lights. I understand the roads are likely to be clearer in April, but the nights are longer in March! Any insight as to if late Winter (March) might have more cloudy nights than early Spring (April)?
According to climatic averages, Reykjavik (which I've chosen arbitrarily) has an average high of 4 degrees in March (low -1) and 7/1 in April. March has 14 days of rain and April, 11 days. That doesn't comment to clear skies, necessarily, but it seems that as the days lengthen, the skies clear.
However, at that latitude, sunrise and sunset change quickly. On or around March 21, Iceland has equal daylight and darkness, as does the rest of the world, but by April 21, has almost 16 hours of daylight. Bear in mind that the nighttime period isn't equally dark, either, and the longer the days, the less dark the nights are . (Eventually it never quite gets totally dark at all.)