This is the 721st most frequent Hebrew word.
בשיא
"At its peak" or "at the height."
Here, בשיא is used to indicate the peak or highest point of someone's career, metaphorically describing a high level of success.
הוא היה בשיא הקריירה שלו כשהחליט לפרוש.
He was at the peak of his career when he decided to retire.
In this sentence, בשיא refers to the highest or most intense point of nighttime darkness.
האורות זרחו בעוצמה בשיא הלילה החשוך.
The lights shone brightly at the peak of the dark night.
In this context, בשיא conveys the moment of greatest intensity or accumulation of snowfall, describing the situation vividly.