Monthly Weather
Summary
The Weather of December 2010
Coldest December on record; mainly dry and sunny
Spells of exceptionally cold weather during December brought some of the lowest temperatures ever
recorded in Ireland, together with heavy snowfalls in places. There were also short periods of milder
weather, while overall the month was drier and sunnier than normal. Mean air temperatures for the month
were up to six degrees lower than normal in places and it was the coldest December on record almost
everywhere. It was also the coldest of any month at Dublin Airport, Casement Aerodrome and Mullingar,
each with over 50 years of record. The lowest December air temperature ever measured in the country,
-17.5°C, was recorded at the climatological station of Straide, Co. Mayo, on the morning of the 25th, while
Casement Aerodrome’s minimum value of -15.7°C on the same day was the lowest value of any month ever
recorded in the Dublin area. Ballyhaise’s mean monthly temperature of -1.4°C represents the lowest ever
measured in the country for any month; the maximum daily value of -9.4°C at the same station on the 21st
was the lowest daily maximum on record. Between 14 and 24 days with air frost were recorded during the
month, over twice the normal number for December. Almost all parts of the country received snowfall at
times, with most persistent falls over Leinster. Although there was some thawing of lying snow around midmonth, by Christmas Day there was 27cm of snow lying at Casement Aerodrome. Monthly rainfall totals
(including snow melt) were below normal everywhere; heaviest daily falls were on the 26th/27th in the south
and southwest, as bands of heavy rain introduced much milder conditions at the end of the month. There
were between 6 and 11 wetdays during the month at most stations (days with 1mm or more rainfall), around
half of the December average. Sunshine totals varied widely, but it was a very sunny month in the west and
southwest, where both Belmullet and Valentia Observatory recorded their sunniest December on record.
1st to 8th: A north to northeasterly airstream over Ireland brought a continuation of the very cold spell which began
in late November. Wintry showers or longer spells of sleet or snow brought further accumulations of snow,
particularly in eastern, northern and western areas. Daytime temperatures were close to freezing, while minimum
values dropped below -10°C in parts of Leinster, falling below -16°C at Mt. Juliet, Co. Kilkenny, on the 3rd.
9th to 15th: Pressure rose over Ireland as an anticyclone to the southwest moved northwards, bringing mostly dry
but cloudy conditions with light winds. Daytime temperatures rose above freezing, bringing some thawing of lying
snow, but frost remained widespread at night.
16th to 25th: A cold front moving southwards on the 16th re-introduced an arctic airstream across the country.
Bitterly cold northerly winds brought snow showers in many areas, most frequently along Atlantic and Irish Sea
coasts, causing considerable disruption of road and air travel. Freezing conditions persisted for long periods, with the
temperature remaining below 0°C for nine consecutive days in some inland areas.
26th to 31st: Frontal systems gave spells of rain on the 26th and 27th, heavy over Munster and Connacht, while
bringing considerably milder Atlantic air across the country, leading to a rapid thaw of lying snow in most areas.
Mild, cloudy and damp conditions for the remainder of the period, with widespread mist or fog.
Wind and elements: Winds were relatively light for most of the month, and mean windspeeds of between 5 and 12
knots (9 and 22km/h) were below normal everywhere; the month’s highest gust of 51 knots (94km/h) was recorded at
Malin Head on the 17th. Hail and snow were frequent in the periods 1st to 8th and 16th to 26th, while most
thunderstorms were recorded near eastern and southern coasts between the 19th and 23rd.
Extreme values at synoptic stations
Rainfall
Highest total: 108mm at Valentia Observatory
Lowest total: 25mm at Gurteen
Highest daily rainfall: 49.2mm at Valentia Observatory on 26th
Temperature
Highest mean monthly temperature: 3.8°C at Malin Head (its coldest December since 1981)
Lowest mean monthly temperature: -1.4°C at Ballyhaise (the lowest mean monthly value on record in the country)
Highest temperature: 12.9°C at Shannon Airport on 28th
Lowest air temperature: -15.7°C at Casement Aerodrome on 25th (its lowest such value since temperature records began there in 1958)
Lowest grass minimum temperature: -17.3°C at Gurteen on 21st (the lowest such value for December in the country since 1961)
Sunshine
Highest monthly total: 91 hours at Valentia Observatory (its sunniest December since records began there in 1892)
Lowest monthly total: 38 hours at Casement Aerodrome
Highest daily sunshine: 7.5 hours at Cork Airport on 8th (its highest daily value for December since 1997)
December 2010
Daily values at selected synoptic stations
Rainfall (mm)
49
25
20
15
10
5
0
1
2
3
4
5
6
7
8
9 10 1 1 12 1 3 14 1 5 16 1 7 18 1 9 2 0 21 2 2 23 2 4 25 2 6 27 2 8 29 3 0 31
7
8
9 1 0 11 1 2 13 1 4 15 1 6 17 1 8 19 2 0 21 2 2 23 2 4 25 2 6 27 2 8 29 3 0 31
Sunshine (hourrs)
8
6
4
2
0
1
2
3
4
5
6
Maximum temperature (°°C)
15
10
5
0
-55
1
2
3
4
5
6
7
8
9 1 0 11 12 13 1 4 1 5 1 6 17 18 19 2 0 2 1 2 2 23 24 25 2 6 2 7 2 8 29 30 31
Minimum temperature (°°C)
15
10
5
0
-55
-11 0
-11 5
1
2
3
z
4
5
6
7
8
9 10 1 1 12 1 3 1 4 15 1 6 1 7 18 1 9 2 0 21 2 2 2 3 24 2 5 2 6 27 2 8 29 30 3 1
Valentia Observatory
z
Dublin Airport
z
Belmullet
December 2010
Percentage / Difference from 1961-90 monthly normals
Rainfall (% of normal for period 1961-1990)
Bel mullet
73
Ballyhaise
54
Carlow
61
Casement Aero
89
Claremorris
48
Cork Airport
49
Johnstown Castle
74
Malin Head
72
Mullingar
40
Shannon Airport
26
Valentia Observatory
67
0
25
Temperature
50
75
100
125
(°C difference from normal for period 1961-1990)
Belmullet
-3.5
Carlow
-6
Casement Aero
-5.8
Claremorris
-5.5
Cork Airport
-4.3
Johnstown Castle
-3.8
Malin Head
-2.5
Mullingar
-5.8
Shannon Airport
-5.6
Val entia Observatory
-3.9
-7
-6
Sunshine
-5
-4
-3
-2
-1
0
(% of normal for period 1961-1990)
Belmullet
257
Casement Aero
80
Cork Airport
166
Dublin Airport
116
Shannon Airport
123
Val entia Observatory
248
50
100
150
200
250
300