The temperature in Ireland is rather moderate as compared to other countries that are located at the same latitude. This temperature pattern is primarily due to the moderating effect of the Atlantic Ocean. Although the entire country is affected by this moderating effect, you may notice that coastal areas are more directly influenced and so therefore have a more consistent temperature.
Inland regions do experience more of a variation in temperature however even in the middle of the country there may only be one day annually that there may be temperatures lower than freezing point. Additionally, while the temperature may drop lower than freezing on any given winter day, it tends not to stay below freezing.
In and around the coastal areas, the temperature drops to below freezing for only about 10 days in a year while in the central areas the average is about 40 days.
Air temperature is typically measured at a height of about 1.2 meters. It is generally measured over flat areas which are covered with short grass. A Stevenson Screen is used to house the thermometers. This is a wooden louvered shelter which has been painted white.
Temperature extremes do occur. The highest air temperature recorded in Ireland was on the 26th of June, 1887. A high of +33.3°C was recorded Kilkenny Castle. The record high for air temperature in the 20th Century occurred Boora in County Offaly on June 29, 1976. Extreme low temperatures have also been recorded. The lowest air temperature on record occurred in 1881. Markree Castle in County Sligo recorded a record low of -19.1°C on the 16th of January. In the 20th Century, the lowest air temperature on record was recorded on the 2nd of January, 1979. It was recorded at Lullymore, County Kildare.
Grass temperature can also be measured. The lowest grass temperature on record was -19.6°C recorded at Dublin on 12th of January, 1982.
The charts below graphically illustrate temperature differences in Dublin (on the East Coast), Valentia Observatory (on the southwest coast) and Birr (which is centrally located). There are two parts to the graphs. The solid bars illustrate the difference between the mean daily high and low temperatures. The thinner lines take the daily ranges of minimum and maximum temperatures and show the range of these temperatures over a thirty year period. The data expressed in these charts was compiled from daily weather reports that were collected between 1971 and 2000 inclusively.