Mud season (US English) orbreakup (Canadian English) is a period in late winter and early spring when travel over ice is no longer safe and travel overland is more difficult as frozen earth thaws and soil becomesmuddy frommelting snow.
Mud season occurs in places where the ground freezes in winter and thaws in spring. Dirt roads and paths become muddy because the deeply frozen ground thaws from the surface down as the air temperature warms abovefreezing. The frozen lower layers of ground prevent water frompercolating into the soil so the surface layers of soil become saturated with water.
Clay-based soil, especially when combined with poor drainage, is especially prone to forming deep and sticky mud. In sandy soils, the top unfrozen layer becomes waterlogged during thaws, but does not form viscous mud. On theGreat Plains, a particular type of clay (bentonite clay, oraluminum phyllosilicate) turns into a sticky form of soil calledgumbo[1] during snowmelt and spring rains.
Mud season can be expensive for towns due to the damage done to dirt roads. One report concluded that the cost of re-engineering dirt roads so that they would remain passable during mud season in the state ofVermont could run as high as $140,000 per mile ($87,000/km).[2]
Transportation problems during mud season have military implications, due to the bogging down of horses and military equipment in deep mud.
During mud season, soil becomes fragile and care must be exercised in protected and recreational areas.[3]
"Breakup" originally referred to the "breaking up" of river and lake ice. This event is eagerly anticipated in manyregions of Canada, because it marks when differentmodes of transportation can be used. Vehicles fromdog sleds tosnowmobiles and eventractor trailers can safely traverseice roads in the winter andaircraft with skis for landing gear can land on ice in winter, but not near breakup. By contrast after breakup, various boats can once again use the water.
The exact date this occurs varies across the North, and corresponds to different seasons in theindigenous calendars of different regions. In theCree andOjibwe calendars, one of the six seasons is calledminoskamin (Woods Cree:ᒥᖪᐢᑲᒥᐣ,mithoskamin;[4]Atikamekw:miroskamin, etc.) which is usually translated as "breakup". For theWoods Cree of Northern Saskatchewan this occurred in roughly May and June on the English calendar before the effects ofrecent climate change. By contrast the New England mud season of (or "unlocking" asKurt Vonnegut called it) is in March and April.[5]
Famously, the exact date of the breakup on theYukon River inDawson City has been the subject ofgambling since theKlondike Gold Rush, providing climate researchers with a rare unbroken record of climate data in such a remote region.[6]
The sense of "breakup" was later expanded to the time of the year when the frozen soil that can support heavy vehicles softens. This is especially used in theoil patch (which is concentrated on the Great Plains and western portions of theboreal forest of Canada (i.e. theWestern Canadian Sedimentary Basin) when well drilling activity halts andwork camps "break up" for the spring.[7][8]
The termmud season is used in northern climates in North America, particularly in ruralnorthern New England and the northern areas of theGreat Lakes. It is often jokingly called the "fifth season".[9] While significantly muddy conditions also occur throughout the Appalachians and in other mountainous regions, they are not as tightly tied to season.
Similar terms are Swedishmenföre "bad going" and Finnishkelirikko "broken state of roads" (lit. "weather-break"), but both also apply to when water is too iced over for boats but not strong enough to cross on foot or in other vehicles. Finnish eastern dialects also have the loanwordrospuutto (IPA:[ˈrospuːtːo]), which has the same usage asrasputitsa.[10]
TheRasputitsa in Russian (literally "season of bad roads"[11]), orBezdorizhzhya in Ukrainian,[12] is a term for the mud season that occurs in various rural areas ofEastern Europe,[12] when the rapidsnowmelt or thawing of frozen ground combined with wet weather in Spring, or heavy rains in the Autumn,[11][13] lead to muddy conditions that make travel on unpaved roads problematic and even treacherous.[11][13]
Rasputitsa has repeatedly "rescued" Russia during wars by causing enemy vehicles and artillery pieces to become mired in the mud, and has been credited, alongside the general conditions of winter, with incumbering both the military campaigns ofNapoleon andHitler in the 20th century, as well asPutin in his2022 invasion of Ukraine.[13]
Further back in history, the Mongols may also have been deterred from attackingNovgorod by the muddy bog produced by an early spring thaw.[14]
Prior to theRussian invasion of Ukraine, some analysts identified the logistical challenges of the mud season as a likely hindrance to any large-scale invasion in spring.[15] When Russia crossed the border, many of its mobile units found themselves stranded in fields and limited to major roads, where resistance and logistical issues significantly slowed the advancetoward Kyiv and elsewhere.[16][17][18]
InMaine,Vermont,upstate New York, andNew Hampshire, the phrase "mud season" can be used as a shorthand reference to the vicissitudes and peculiarities of life in the region. The term has been used as the title of magazines,[19] books,[20] and at least one movie.[21]
During the Mongol invasion of the Rus' principalities in 1238-1240, Novgorod escaped destruction by the Mongols due to an early spring, which transformed the routes to Novgorod into a muddy bog.
