Ash tree spring budding

Ash trees of north side of street leaf out about 1 week before those on the south side.  What you can’t see is that there is a parking garage that shades the trees on the south side.  As a result the north side is warmer and therefore brings out the buds on the trees more than a full week before the trees across the street even though they were all planted at the same time, are the same age and are in very similar soils.