The tripod on the Tanana river at Nenana fell over on April 27, 2024, at 05:18 am, triggering the clock that ends this year’s Nenana Ice Classic. The long standing tradition of betting on the day and time of the river break up at Nenana has produced a long and unique climatological time series of river break up dates.

Below is a graph of the Nenana Ice Classic break up dates through 2024. Data is plotted as decimal days of year to avoid a shift in leap years. The axis labels are given as dates for easier interpretation. May first is the 121st day of the year in regular years and the 122nd day of the year in leap years. Average break-up dates for the climate reference periods 1931-1960, 1961-1990 and 1991-2020 are plotted as colored lines for reference.

This year’s break up date (April 27) is about two days earlier than average when compared to the 1991-2020 reference period and  a week ahead of the 1931-1960 and 1961-1990 reference periods. The earliest break up date of the time series occurred on April 14, 2019. The latest break up occurred on May 20, 1964.