Extremely low temperature

Region/Country	Description
US	A freeze is when the surface air temperature is expected to be 32°F or below over a widespread area for a climatologically significant period of time. Use of the term is usually restricted to advective situations or to occasions when wind or other conditions prevent frost. "Killing" may be used during the growing season when the temperature is expected to be low enough for a sufficient duration to kill all but the hardiest herbaceous crops. Frost describes the formation of thin ice crystals on the ground or other surfaces in the form of scales, needles, feathers, or fans. Frost develops under conditions similar to dew, except the temperatures of the Earth's surface and earthbound objects falls below 32°F. As with the term "freeze," this condition is primarily significant during the growing season. If a frost period is sufficiently severe to end the growing season or delay its beginning, it is commonly referred to as a "killing frost." Because frost is primarily an event that occurs as the result of radiational cooling, it frequently occurs with a thermometer level temperature in the mid-30s. Increased wind speeds accelerate heat loss from exposed skin. No specific rules exist for determining when wind chill becomes dangerous. As a general rule, the threshold for potentially dangerous wind chill conditions is about -20°F.
DE	Überörtlich oder anhaltend Lufttemperatur < -10 Grad in Lagen bis 800m Verbreitet Lufttemperatur unter dem Gefrierpunkt in der Zeit vom 01.04. bis 31.10. jeden Jahres, in Lagen bis 800m.
AU	Frost Warning.
CA	A Frost Warning is issued or referenced in the public forecast only when air temperatures are expected to fall to near freezing or below during the local growing season, as early as April 15th to October 15th in southern British Columbia and for shorter periods elsewhere in Canada. A frost warning would normally be issued when forecast air temperature is +2°C or below. An Arctic Outflow Warning is based on a combination of wind speed and temperatures which produce wind chills of at least -20 for at least six hours. When a Wind Chill Warning is issued, expect very cold temperatures combining with wind to create outdoor conditions hazardous to human activity. Wind chill warning criteria vary across the country, ranging from -55 in some arctic regions to -30 in southwestern Ontario. Warnings will be issued when the winds are expected to be at least 15 km/h and these extreme wind chills will persist for at least three hours. When temperatures are expected to fall dramatically within 24 hours from above normal or near seasonal temperatures to very cold temperatures a Cold Wave Warning is issued in some parts of the country. Drop of 12 degrees Celsius or more in 3 hours with winds of more than 30 km/hr; then the final temperature should be less than zero Celsius. Wind chill factor between -30 and -39 at least during 6 hours or more for public forecast regions in FPCN71 CWUL, FPCN73 CWQB AND FPCN74 CWXK. When the factor is between -35 to -49 for 6 hours or more for public regions in FPCN72 CWQB Wind chill factor lower or equal to -40 during 6 hours or more for regions in FPCN71 CWUL, FPCN73 CWQB and FPCN74 CWXK. For regions in FPCN72 the wind chill factor should be lower or equal to -50 for at least 6 hours.
EU	Low Temperature, Extreme low temperature.
JP	Frost, Low Temperature.