At various times or in a series of data, the presence of variations that occur at specific regular intervals in less than a year; such as, weekly, monthly, or quarterly: Seasonality may be caused by various factors; such as, weather, vacations, or holidays and it consists of periodic, repetitive, and generally regular and predictable patterns in the levels of a series in times.

Some people track the seasonality of rainfall levels or snow levels, etc. during certain times of the year.