There have been several challenging years for the Birkie classic event, most notably 2002, 2014, and 2016. Some have called 2014 the hardest Birkie year ever, but this is mostly coming from those doing the freestyle event. The 2014 race was accompanied by heavy snowfall. According to American Birkebeiner & Kortelopet – 1973 to Present, temps hovered around 10 below zero at the start, and nearly 18 inches of snow fell throughout the two days before the event. The snow was groomed throughout the night and was pushed off the trail in some sections to create the best skiing conditions possible.
It rained the day before the race in 2016, and it was warm and slushy, which slowed things a bit.
The real standout for the classic race was 2002, which was dramatically slower than most other years. Snow was scarce until about four days prior to the race when 8” of new snow covered the course. The freestyle and classic races were held on the same course during this period, so classic skiers faced more difficult conditions than after 2008 when the separate classic course was set.
The fast years were 2010, 2012, and 2020. Cold, firm, well-set tracks were the likely cause. Temperatures were moderate for most of the race, and in 2020, in particular, the classic tracks stayed very solid, at least for the early waves.
There is a great website that provides a full suite of anecdotal accounts of Birkie races from 2011 to 2025 – BirkieGuide.com by Ari Ofsevit.