«زَي لَيَالِي الشِّتَا طَوِيلَهْ وْبَارْدَهْ»

The expression holds up winter nights, which are at once long and cold, as a measure for something else. Whatever it is applied to is marked as extremely cold and extremely heavy, with the length of those nights lending the image its sense of weight.

The comparison works through excess and keeps both traits in view rather than reducing the image to temperature alone. It is not meant for a mild chill or a slight burden but for something that reaches the furthest degree of both coldness and heaviness at once.

Apply it when describing something whose coldness and heaviness are both extreme, with long, cold winter nights serving as the yardstick. It fits cases where the two qualities appear together and in excess, not where only one is present or the degree is slight.