Steenburgh winter is different from astronomical winter, which extends from the winter solstice to the spring equinox. Steenburgh winter is based on ski conditions.
Steenburgh winter begins the first day that the Alta-Collins snow stake reaches 100". That's a big number, but it represents the approximate snow depth needed to transition from early season conditions to winter conditions in the Cottonwoods. Some might think this is high, but it is roughly when most of the brush, pucker trees, and big, angular boulders are buried in the backcountry. Case in point, the Alta-Collins snow depth is just under 70", yet I hit a buried pucker tree this weekend and took quite a digger. That is a rare event once we reach a 100" base.
Steenburgh winter ends on February 10. Why February 10? It seems to be around this time of year when the sun begins to have an increasingly caustic effect on powder. Resort skiers don't notice this change (they track everything out too quickly), but backcountry skiers do. Prior to February 10, powder can linger for many days on most aspects. Even south facing slopes might survive without a melt-freeze cycle if it is really cold. After February 10, the south aspects will almost always suffer a melt-freeze cycle if the sun comes out and, as the days go on, the sun becomes an increasingly formidable enemy to powder on an increasingly greater range of aspects.
There is certainly good skiing to be had after 10 February, but it does represent an important transition point in the snow climate of the Wasatch. Therefore, it marks the end of Steenburgh winter.
This year we have a 65" base at Alta-Collins on February 10th. Hence, this is a year without a Steenburgh winter.
Graphic Source: http://www.classroomjr.com/weather-coloring-pages/melting-snow-coloring-page/