Exceptionally Cold December

Armagh Observatory reports that December was much colder, sunnier and drier than average.

The mean monthly temperature was –0.3 degrees Celsius (31.4 degrees Fahrenheit), about 5.4 Celsius below average, making December 2010 the second coldest December in Armagh since records began around 1795. The three coldest Decembers in Armagh are now those of 1878, 2010 and 1796, with average temperatures of -0.5 C, -0.3 C and 0.6 C respectively.

The maximum air temperature was 10.8 C on the 28th, whilst the lowest air temperature was –11.9 C on 21st, making the morning of the winter solstice the fourth coldest December night in Armagh since records of daily temperature maxima and minima began in August 1843. Previous cold December nights were -14.6 C on Christmas Day 1878, -13.7 C on Christmas Eve 1878, and -12.2 C on December 20th 1886. In 2010 there were twenty-four nights with grass frost and twenty-four with air frost, with snow falling on six days.

The winter solstice, December 21st, was also the coldest day since 1843, with a maximum temperature of –8.0 C and an average temperature of -10.0 C. This was probably the coldest day in Armagh since the very cold 13th January 1814, which with morning and evening temperatures of -12.2 C and -13.3 C reportedly had `the hardest frost recorded here for the space of 20 years’.

The number of hours of sunshine was 48.7, that is, about one-third more than the monthly average, though this is probably underestimated as a result of frost and snow. The total precipitation for the month was 37.7 mm (1.48 inches), that is, about 45% of the average. Taken as a whole, the average temperature for 2010, namely 8.74 degrees Celsius, was much lower than the peak of 10.62 C reached in 2007, making 2010 the coldest year since 1986 (annual average temperature of 8.62 C). However, total precipitation for the year, around 796 mm, while slightly drier than that of recent years, was close to the long-term average.

These data refer to observations at Armagh Observatory, which has been recording the weather at Armagh since 1795.

FOR FURTHER INFORMATION PLEASE CONTACT: John McFarland at the Armagh Observatory, College Hill, Armagh, BT61 9DG. Tel.: 028-3752-2928; FAX: 028-3752-7174; jmfat signarm.ac.uk; URL: climate.arm.ac.uk.

Last Revised: 2011 January 2nd