Late summer snows are not unusual. However, they tend to be brief and not particularly damaging to agriculture (I: 34. SSM: 1)
It is said that it grows so cold in the north that a man's laughter freezes in his throat and chokes him to death (I: 39)
In the south, the northmen are said to be made all of ice and melt in the southron heat (I: 162)
Rain falls cold and hard, and sometimes turns into hail that can send men running for cover and ruin crops, even during a summer (I: 238)
Bronze and iron were the metals of the north, strong and dark to fight the cold (II: 79)
Once the autumn is declared by the maesters, the lords of the North store away a part of the grain they have harvested. How much is a matter of choice; between one fifth and one fourth seems prudent, however (II: 184)
The Ice Dragon (its name may be different outside of the North) is a constellation used to help mark direction, because the blue star in the rider's eye points the way north (II: 381)
Even in the deep of the wolfswood there are foresters, crofters, and hunters (III: 105)
The northmen have long memories. A lord who does not seek his rightful vengeance threatens to have his own men turn on him (III: 229)
It's said a maiden girl could walk the kingsroad in her name-day gown and still go unmolested, and travelers could find fire, bread, and salt at many an inn and holdfast (III: 276)
Heraldry in the North is significantly simpler and more basic than that in the South, showing the differing amounts of influence that chivalry has had there (SSM: 1)
In the North, food is smoked, salted, and otherwise preserved ahead of winter. Lords keep "glass gardens" to try and supply their own castles even in winter. Coastal communities depend on fish, although even in winter ice fishing is common on the rivers and Long Lake. Poor harvests before winter will mean famine, however. (SSM: 1)
Houses descended of the First Men tend to have short, simple, descriptive names (SSM: 1)
The North and the Vale are approximately on par when it comes to military strength. However, the North's population is spread over a much greater area, and harvests are even more important when colder seasons draw near (SSM: 1, 2)