May through September offers the best combination of mild temperatures (55–68°F), long daylight hours, and the full summer festival calendar. June and July are the driest months, though 'dry' in Ireland means rain is still possible any day. March brings St. Patrick's Festival crowds and festive energy. October and November are uncrowded, prices drop, and the autumn colours in Wicklow and Glendalough are spectacular. December through February is the quietest period — expect short days, raw Atlantic winds, and some coastal tour operators operating on reduced schedules.
| Month | High (°F) | Low (°F) | Notes |
|---|---|---|---|
| Jan | 46 | 38 | cool & changeable |
| Feb | 47 | 38 | cool & changeable |
| Mar | 50 | 39 | cool & changeable |
| Apr | 54 | 42 | cool & changeable |
| May | 59 | 47 | cool & changeable |
| Jun | 64 | 52 | mild & changeable |
| Jul | 66 | 55 | mild & changeable |
| Aug | 65 | 55 | mild & changeable |
| Sep | 62 | 52 | mild & changeable |
| Oct | 57 | 48 | cool & changeable |
| Nov | 50 | 43 | cool & changeable |
| Dec | 47 | 39 | cool & changeable |