How we know: Sources are listed at the end. Weather figures are official climate normals; route and border facts come from the cited references. Wildly does not publish fare averages in prose; live prices are on the linked route pages.
Ireland does not have a bad season so much as a short-days season. The weather is mild and changeable all year, with Wikivoyage's summary that you may get "four seasons in one day" holding in every month. What changes is daylight, which runs from under eight hours in December to about seventeen in June, and crowds, which peak in July and August. For the classic west-coast drive, May, June and September give long days, everything open, and fewer tour buses. For a Dublin city break, any month works, and the winter months are when transatlantic demand is lowest.
Dublin weather by month
Official 1991–2020 climate normals for Dublin Airport, from Met Éireann. The west (Galway, Kerry) is noticeably wetter; the sunshine column is the more useful guide to what a day feels like.
| Month | Avg high | Avg low | Rain | Sunshine | |---|---|---|---|---| | January | 46°F (8°C) | 36°F (2°C) | 2.4 in | 59 hrs | | February | 47°F (9°C) | 36°F (2°C) | 2.1 in | 81 hrs | | March | 50°F (10°C) | 37°F (3°C) | 2.0 in | 115 hrs | | April | 54°F (12°C) | 39°F (4°C) | 2.2 in | 161 hrs | | May | 59°F (15°C) | 44°F (7°C) | 2.2 in | 199 hrs | | June | 64°F (18°C) | 48°F (9°C) | 2.5 in | 179 hrs | | July | 67°F (20°C) | 52°F (11°C) | 2.4 in | 157 hrs | | August | 66°F (19°C) | 52°F (11°C) | 2.9 in | 156 hrs | | September | 62°F (17°C) | 49°F (10°C) | 2.5 in | 131 hrs | | October | 56°F (14°C) | 45°F (7°C) | 3.1 in | 105 hrs | | November | 51°F (10°C) | 40°F (4°C) | 3.3 in | 73 hrs | | December | 47°F (8°C) | 37°F (3°C) | 2.8 in | 54 hrs |
The temperature range is tiny: average highs never leave the 46–67°F band. Rain falls in every month and is actually a little lower in spring than in summer; May is the sunniest month on average. Wikivoyage's practical advice applies year-round: pack a waterproof, and expect rain even in mid-summer.
Season by season
November–February (winter). Short days (sunset around 4:30pm in December), quiet roads, and the lowest visitor numbers. Dublin, Cork and Galway run normally; some rural attractions and B&Bs close or cut hours. Christmas week aside, this is the quiet season for US–Ireland flights.
March–May (spring). Daylight stretches fast, the countryside greens up, and most seasonal attractions reopen by Easter. St Patrick's Day (17 March) fills Dublin for the surrounding week. May is the sunniest month on average and one of the best for the Wild Atlantic Way.
June–August (summer). Longest days and the busiest period on the Ring of Kerry, Cliffs of Moher and Dingle. Weather is mild rather than hot, with August the wettest of the three. Book coastal lodging well ahead.
September–October (autumn). September keeps much of summer's daylight and warmth with far fewer visitors. October turns wetter and shorter, with good colour in Wicklow and West Cork.
Getting there from the US
Dublin (DUB) has the densest US network of any Irish airport, with Shannon (SNN) as the western alternative. Wikivoyage's Dublin Airport guide lists Aer Lingus on 13 US routes, including Boston, New York JFK, Newark, Chicago, Philadelphia, Washington Dulles, Hartford, Minneapolis, Orlando, Miami, Los Angeles, San Francisco and Seattle; American from Chicago, Dallas/Fort Worth and Philadelphia; Delta from Atlanta, Boston and JFK; and United from Chicago, Newark, San Francisco and Washington. Several of these are seasonal, so check the schedule for your dates.
Dublin is also the only hub airport in Europe with US Border Preclearance (Wikivoyage): you clear US immigration and customs before boarding, and land in the US as a domestic arrival. It adds time before departure and saves it on arrival.
For current prices see JFK to Dublin, Boston to Dublin, Newark to Dublin and Chicago to Dublin, or compare all US origins on the flights to Dublin hub.
When fares tend to be lowest
US–Ireland is a leisure-heavy market with strong family and heritage travel, so demand peaks in June–August, around St Patrick's Day, and over Christmas and New Year. The quiet windows are usually mid-January through early March (outside the St Patrick's week) and November. Ireland's short flight time from the East Coast and heavy competition into Dublin mean spring and autumn fares are often reasonable too, but seasonality still rules.
Set a price alert for your route and dates. Wildly checks prices daily on the routes you track and emails you when the fare drops to your target; the route pages above show recent prices so you can pick a realistic one.
Entry requirements for US citizens
Ireland is not in the Schengen Area and runs its own immigration rules. US citizens may enter without a visa for visits of up to 90 days (Wikivoyage, "Ireland — Get in"). You will clear Irish immigration even if Dublin is only a connection to mainland Europe, and time spent in Ireland does not count against the Schengen 90-day limit. Northern Ireland is part of the UK; there are no border checks on the island, but check that a rental car may be taken across.
Where to go, by season
- Winter: Dublin (museums, distilleries, theatre), Cork and Kinsale for food, Belfast.
- Spring: Wild Atlantic Way from Kerry to Connemara before the coaches arrive; Wicklow and Glendalough.
- Summer: Aran Islands, Achill, Donegal and the Antrim coast, which absorb crowds better than Kerry.
- Autumn: The classic Dublin–Galway–Kerry–Cork loop in September; West Cork and Wicklow for colour in October.
FAQ
What is the best month to visit Ireland? May, June or September: long days, mild weather, everything open, and fewer visitors than July–August. May is the sunniest month on average.
How much does it rain? Every month has rain, but Dublin's monthly totals are modest (2–3.3 inches). The west gets considerably more. Showers are the norm rather than all-day rain.
Do I need a car? Not for Dublin. For the west coast, yes; public transport reaches the towns but not the coastal viewpoints. Ireland drives on the left.
Is Dublin preclearance worth it? It makes the US arrival painless, particularly with a domestic connection. Allow extra time at Dublin for the second security and immigration check.