Dublin weather in September
September in Dublin: nice, a little rain, with clean air — an excellent time to visit.
Updated September 2026 · climate normals from ERA5 reanalysis
#5 of 12 months in Dublin · #677 of 1413 destinations to visit in September · comfort 80/100 (tier A)
- Days
- 18°C
- Nights
- 10°C
- Wet days
- 13
- Sun
- 7.9 h
- Humidity
- 81%
- Daylight
- 13 h

Traveller notes on Dublin in September
Other months in Dublin
Regulars call this a genuinely lovely month, with long, bright days and temperatures that rarely turn genuinely cold, calling it usually one of the more consistent months weather-wise here - though the standard caveat holds that Irish weather can never be fully trusted. Our row backs the mild read, 16.9C over 8.3C nights feeling 6C, with 45.7mm of rain across 9.5 days. Regulars describe a single day capable of running cool, rainy, sunny and warm in turn, so layers plus a waterproof jacket or umbrella remain the standard advice even in this comparatively reliable month. The sea sits at a cool 13.8C. The record: humidity 78 percent, 11.1 hours of sun, an 18.4 kph wind and AQI 39.
The only thing regulars will guarantee about June here is the light: bright from just after five in the morning and still bright at half past ten at night. Our daylight column says 16.9 hours; their eighteen counts the long twilight either side, which in fine weather is usable time. The weather inside it changes within the hour, from sunshine to downpour and back, so layers and a rain shell whatever the forecast says - our 58.7mm falls across 10.5 days. Temperatures are mild rather than warm, 19.2C over 11C. Bloomsday is the 16th and is smaller than visitors expect. The record: humidity 77 percent, 10.8 hours of sun and AQI 35.
Sunshine and showers is the phrase regulars keep for August here, with the note that thundery short downpours are likelier this month than any other and that nobody knows anything until it arrives. Our row is kinder than the figures they quote - 20.5C over 12.5C against their 15 to 18C and lows in the single digits, which describes a cold late-August night rather than a normal one. Rain falls 60.4mm across 11 days, about five millimetres a time: showers, as advertised. Their packing list is a hooded lightweight waterproof rather than an umbrella, layers, and something for a cool night. A 20.2 kph wind is why the hood matters. The record: humidity 79 percent, 9.4 hours of sun and AQI 30.
July is Dublin's warmest and busiest month and the forum's advice is almost entirely about clothes. Daytime temperatures across the month run anywhere from about 14 to 27C, and the honest summary is that they cannot be predicted: expect rain and sunshine inside a few hours, and carry a light rain jacket regardless, because it will rain. July and August are also the worst of the crowds, with May and September named as the alternative that trades a little warmth for a lot of space. The record: 20.8C days that feel like 20C, 12.7C nights, 11.3 precipitation days carrying 68.1mm and a 16.4-hour day.
Year-round notes are on Dublin's overview. Add your own note from Dublin's card on the map.
Dublin climate normals — September
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Dublin in September
How busy the place itself is — school and mass holidays, the months an editor tagged, and how sought-after the weather makes them. Never part of the comfort score.
Shoulder seasonschool holidays in 3 of the markets that fill it, an ordinary month(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for Dublin's weather
Ranked by this destination's own climate comfort score across the year — a different thing from how busy it gets (see Crowds above).
Fair weatherDublin's weather peaks June–August, best around July.
Best weatherFair weatherToughest weather
What's on in Dublin in September
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Rule
Book of Kells timed tickets
1 Jan – 31 DecBook earlyTrinity sells dated, timed slots for the Book of Kells and the Old Library, and the summer mornings go days ahead. The Long Room has been through a long conservation project, so check what is actually on show. Source ↗
- Festival
Culture Night
15–25 Sep · usuallyMajor festivalOne Friday in September when several hundred buildings — studios, embassies, the odd government office — open late and free. The ones with small rooms need queueing for early. Source ↗
- Festival
Dublin Theatre Festival
24 Sep – 11 OctArts festivalBook earlyA fortnight from late September across the Abbey, the Gate and a dozen smaller rooms. The shows people talk about afterwards sell out before the festival opens. Source ↗
Nearby, and something's on
Within 300 km of Dublin — a day trip or a short hop — with something on this month. Never part of the comfort score.
Where is Dublin?
Dublin in September — FAQ
- Is September a good time to visit Dublin?
- September in Dublin: nice, a little rain, with clean air — an excellent time to visit. It ranks #5 of 12 months for Dublin on SeasonMap's comfort score (80/100).
- What is the weather like in Dublin in September?
- In September, Dublin averages a daily high of 18.1°C and a low of 10.4°C, with about 78.5 mm of rain over roughly 13.1 rainy days.
- What is the air quality in Dublin in September?
- Dublin has a mean US Air Quality Index of about 36 in September.
Within 300 km: Belfast's Culture Night on 18 Sep, and Liverpool's International Beatleweek on 26 Aug – 1 Sep.