The dominant influence on Ireland's climate is the Atlantic Ocean. Consequently, Ireland does not suffer from the extremes of temperature experienced by many other countries at similar latitude.
Average annual temperature is about 9°C. In the middle and east of the country temperatures tend to be somewhat more extreme than in other parts of the country. For example, summer mean daily maximum is about 19°C and winter mean daily minimum is about 2.5°C in these areas.
Mean annual windspeed varies between about 4 m/sec in the east midlands and 7 m/sec in the northwest. Strong winds tend to be more frequent in winter than in summer. Sunshine duration is highest in the southeast of the country. Average rainfall varies between about 800 and 2,800mm.
With southwesterly winds from the Atlantic dominating, rainfall figures are highest in the northwest, west and southwest of the country, especially over the higher ground. Rainfall accumulation tends to be highest in winter and lowest in early summer.
The annual number of days with more than 1 mm of rain varies between about 150 in the drier parts and over 200 in the wetter parts of the country.
Air temperatures are measured at a height of approximately 1.2 m above a flat surface covered with short grass. The thermometers are housed in a white painted wooden louvred shelter known as a Stevenson Screen.
The moderating influence of the Atlantic is felt throughout Ireland. The country therefore does not experience the same range of temperatures through the year as more continental countries. Though our inland stations show more variation, even at these there would only be about one day or less per year when the air temperature stays below freezing point. Minimum air temperature falls below zero on about 40 days per year at the inland stations but on less than 10 days per year in most coastal areas. Air temperatures inland normally reach 18 to 20 ºC during summer days, but only about 8 ºC during wintertime.
Regarding extremes, the highest air temperature recorded in Ireland was + 33.3ºC at Kilkenny Castle 26th June 1887. The record maximum during the 20th century is +32.5ºC at Boora, Co. Offaly on 29th June 1976. The lowest air temperature was -19.1ºC measured at Markree Castle, Co. Sligo on 16th January 1881 while the lowest observed 20th century air temperature was -18.8ºC recorded at Lullymore, Co. Kildare on 2nd January 1979. The lowest observed grass minimum temperature was -19.6ºC at Dublin (Glasnevin) on 12th January 1982 which was almost matched by the -19.5ºC measured at Lullymore, Co. Kildare on 2nd January 1979.