There is no bad month to visit Ireland, but there are months that suit different trips, and the gap between them is bigger than the weather forecast suggests.
The short answer
May and September are the best months. Long days, most attractions open, prices below peak, and crowds that have either not arrived or just left. If you can only go in July or August, you will still have a good trip — you will just share it.
Month by month
January and February. Cheap, dark and quiet. Sunset before five. Many rural attractions and some restaurants close entirely. Good for cities, poor for coastlines.
March. St Patrick’s Day fills Dublin and pushes prices up for about a week. Outside that, still low season. Weather is unreliable but the light is coming back.
April. Things reopen. Gardens start to look like themselves. Easter can be busy, otherwise this is a quietly good month with real risk of rain.
May. Arguably the best. Statistically the driest month in much of the west, long evenings, everything open, and the hedgerows are extraordinary. Book ahead for the bank holiday weekends.
June. Daylight until half ten at night, which changes what you can fit into a day. Busier than May, not yet peak.
July and August. Peak. Warmest, busiest, most expensive, and the only time you must book accommodation months ahead in Kerry, Clare and Galway. Irish schools are off, so domestic tourism adds to it.
September. The other best month. Sea is at its warmest, crowds thin after the first week, prices drop, and the light gets golden. Our pick if you have a free choice.
October. Beautiful and increasingly wet. Attractions start closing mid-month. Good for cities and the east.
November and December. Dark and quiet, with Christmas markets in the cities from late November. Not a touring month.
The thing the averages hide
Irish weather is not seasonal in the way most visitors expect. It is maritime, which means it changes hour to hour rather than month to month. A July day can be grey and 14 degrees. An April day can be still and bright. The practical consequence: pack for all of it whenever you come, and build a route that works wet or dry.
The other consequence is that the “best month” question matters less than the “how long do I stay in each place” question. A week in one region in November will beat a fortnight of driving in June.
If you are choosing right now
Go in May or September if you can. Go in June if you want the longest days. Avoid the last week of July and first week of August unless you have already booked. And whichever month you pick, assume you will get one properly wet day in every four and plan something indoors for it.