The moderating influence of the Atlantic is felt throughout Ireland. The country therefore does not experience the same range of temperatures throughout the year as more continental countries do. Although our inland stations show more variation, even at these there is only 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 °C during summer days, and about 8 °C during wintertime.

Some of these variations are shown graphically in the diagrams for Dublin (east coast), Valentia Observatory (southwest coast) and Birr (inland). In these graphs the solid bars show the difference between the mean daily minimum and maximum for the month in question and the thinner lines indicate the range of daily minima and maxima observed over a thirty year period. The graphs are based on daily reports from 1971 to 2000 inclusive.

Regarding extremes, the highest air temperature recorded in Ireland was + 33.3°C at Kilkenny Castle 26th June 1887. The record maximum during the 20th century is +32.5°C at Boora, Co. Offaly on 29th June 1976. The lowest air temperature was -19.1°C measured at Markree Castle, Co. Sligo on 16th January 1881 while the lowest observed 20th century air temperature was -18.8°C recorded at Lullymore, Co. Kildare on 2nd January 1979. The lowest observed grass minimum temperature was -19.6°C at Dublin (Glasnevin) on 12th January 1982 which was almost matched by the -19.5°C measured at Lullymore, Co. Kildare on 2nd January 1979.