where the sun don't shine

Half the roof of my garage still has snow on it reflecting a consistennt pattern along the street.

It happens because the half of the roof facing north gets less sun than that facing south. The grade of the roof is quite shallow but so is the angle to which the sun climbs in winter. This means that only the south leaning part of the roof gets any meanigful sun exposure.

It is also rmarkable that the weak winter sun is able to melt snow at a temperature well below freezing.