Ireland has a temperate maritime climate that is influenced both by the warm waters of the Gulf Stream and the southwestern winds of the Atlantic Ocean, known as the prevailing winds. The combination of these two factors results in temperatures that remain fairly consistent across the entire country. The Atlantic Ocean influences the moderating effect by absorbing heat in the summer and releasing it during the winter.
Dubbed the Emerald Isle, the nickname refers to the beautiful green vegetation that adorns the country as a result of the light precipitation that falls year round. The western part of Ireland tends to be wetter on average than the east.
In late autumn and winter months the western areas are also occasionally prone to experience Atlantic storms. These storms can sometimes be severe enough to cause high levels of rainfall and strong winds to these parts of the country, and may bring hail and snow as well.
During the winter months, typical Ireland weather includes clouds and rain with occasional sunshine. Snow falls on low lying areas only a few days a year, while the mountains may have snow on them for many weeks during the winter season.
January temperatures average 5ºC or 41ºF. Frequently overnight temperatures will drop below freezing. Ice and frost are typical of winter weather in Ireland. For a few weeks in the winter months the temperature does not rise above freezing at all during the day. It is not unusual for rivers and lakes to partially freeze over during this time.
A normal summer in Ireland offers warm, sunny days with light clouds in the sky. Summer rain is usually light and occurs on only a few days during the season. Humidity and thunderstorms with lightning occur on occasion during the months of July and August.
The average temperature in July is around 15ºC or 59ºF, but temperatures above 30ºC or 86ºF are not unusual. The southern part of Ireland enjoys slightly warmer weather than the northern areas. The inland areas which are away from the warm ocean waters tend to be the coolest areas.
The southwestern prevailing winds of the Gulf Stream bring temperate conditions in the form of low pressure depressions to what might otherwise be up to 20ºC or 68ºF cooler. An occasional blast of extremely cold weather from the Arctic can bring snow, frost and icy winds.
Although it is unusual, Ireland occasionally receives wind from the east which originates over central Russia where there very little moisture. The result is either hot, dry summer weather, or cold, dry winter weather.
Across the country the local climate differs somewhat from place to place. The mountains and areas east of the mountains generally experience the wettest weather, as in Kerry, Galway and Donegal. Dryer weather is typical of areas such as the east coast where there are fewer mountains. The driest weather occurs in the counties of Dublin and Kildare.
Ireland is widely known for its rich green foliage. The difference in the amount of rainfall throughout the country does not have a significant impact on the type of vegetation. The quantity of rainfall is not as important as the frequency of the rain.