What is permafrost?

Permafrost refers to soil that is frozen all year long, even during the summer, for two consecutive years or more. Such conditions occur in areas where the mean annual temperature is 23°F (-5°C) or less. Construction in polar regions where permafrost is found can be problematic, because sometimes the ground can thaw beneath a building that was constructed over frozen ground; when this happens, building foundations are easily compromised.

Is there much permafrost in the lower 48 U.S. states?

There is no permafrost in the lower 48 states, though states such as North Dakota and Minnesota do often experience conditions where frost levels penetrate the ground to depths extended 30 or more inches (76 centimeters).

Have the Great Lakes ever been completely frozen over?

There have been occasions when the Great Lakes completely froze, which last happened in 1979. In the winter of 1993 to 1994, the lakes almost froze solid, but not completely. Even though this does not happen often, the Great Lakes generally shut down to shipping traffic during the months of January through March because the ice is far too hazardous.

Has the Hudson River ever frozen over?

The Hudson River in New York state extends about 300 miles (483 kilometers) from Lake Tear-of-the-Clouds on Mount Marcy down to New York Bay. When people think of the Hudson, what comes to mind is the part of the river that flows through the New York metropolitan area. This section does not freeze often, the last time being in January of 1918. However, at the higher elevations near the river's source, the Hudson freezes quite regularly.

What are some of the lowest temperatures ever recorded?

The table below lists some of the most chilling temperatures, by region, that have been recorded by meteorologists.

Is Moscow, Russia, colder than Minneapolis, Minnesota?

Moscow is at a latitude of 55° 45', while Minneapolis is at 44° 53'. Nevertheless, they have similar climates. Both cities experience mean January temperatures of about 14°F (-10°C), while Julys are about 66°F (18.9°C) in Moscow and 74°F (23.3°C) in Minneapolis on average.

Low Temperature Records



Temperature (°F/°C)

Vostok, Antarctica



Klinck, Greenland



Oimekon, Russia



Verkhoyansk, Russia



Northice, Greenland



Snag, Yukon, Canada



Ust'Shchugor, Russia



Coyaique Alto, Chile



Sarmiento, Argentina



Ifrane, Morocco



Charlotte Pass, New South Wales, Australia



Mauna Kea Observatory, HI



What are some of the coldest temperatures ever recorded in the United States?

Coldest U.S. Temperatures



Record Low (°F/°C)*

Prospect Creek, AK

January 23, 1971


Tanacross, AK

February 3, 1947


Rogers Pass, MT

January 20, 1954


Peter's Sink, UT

February 1, 1985


Riverside Ranger Station, MT

February 9, 1933


Moran, WY

February 9, 1933


Maybell, CO

February 1, 1985


Island Park Dam, ID

January 18, 1943


Tower, MN

February 2, 1996


Parshall, ND

February 15, 1936


McIntosh, SD

February 17, 1936


Tetonia, ID

February 9, 1933


Couderay, WI

February 4, 1996


What is the best weather for maple syrup to be produced?

Maple syrup harvesters wait until nighttime temperatures dip below freezing, while day temperatures are above freezing. The conditions are ripe for the sap in maple trees to flow best.



Record Low (°F/°C)*

Seneca, OR

February 10, 1933


Old Forge, NY

February 18, 1979


Vanderbilt, MI

February 9, 1934


San Jacinto, NV

January 8, 1937


Gavilan, NM

February 1, 1951


Bloomfield, VT

December 30, 1933


Big Black River, ME

January 16, 2009


*Does not account for wind chill.

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