Killarney weather in September

September in Killarney: cool, rainy, with clean air — an excellent time to visit.

Updated September 2026 · climate normals from ERA5 reanalysis

Killarney🇮🇪 Ireland · British Isles · Trekking81
  1. 64Jan
  2. 66Feb
  3. 73Mar
  4. 82Apr
  5. 90May
  6. 88Jun
  7. 89Jul
  8. 86Aug
  9. 81Sep
  10. 74Oct
  11. 68Nov
  12. 61Dec

#6 of 12 months in Killarney · #652 of 1413 destinations to visit in September · comfort 81/100 (tier A)

Days
17°C
Nights
11°C
Wet days
15
Sun
7.5 h
Humidity
85%
Daylight
13 h
Killarney, Ireland
Photo: Tanita Lupa · Pexels

Traveller notes on Killarney in September

Killarney-forum threads on September weather are direct conditions here can go every direction within the same single day, sun, cloud, a shower and real wind all entirely possible on one outing around the lakes. Posters call short-sleeved layers under a windbreaker the standard advice, shorts generally unnecessary even on a mild afternoon. Regulars describe late August into early September as sometimes running comfortably mild, other years bringing a genuinely wetter stretch, nothing guaranteed one week to the next in County Kerry. Killarney National Park is called worth visiting regardless of forecast, the lakes and mountain backdrop striking even under grey skies. Posters recommend packing for every condition rather than trusting a single forecast more than a day out, air conditioning entirely unnecessary given how mild temperatures stay here. The record: 16.7C days feeling like 15C, 11.2C nights, an extraordinarily high 107mm across over 15 days and 85 percent humidity.
KillarneySeptemberRegular · September · 1 month ago · Read more on Tripadvisor ↗

Other months in Killarney

Killarney-forum threads on visiting the national park in March describe the honest expectation as genuinely unpredictable, posters calling proper layers and real rain gear the standard advice. Regulars describe March as broadly colder and wetter than later spring, several places around town still running a reduced winter schedule. Posters call the Gap of Dunloe walk or cycle route still genuinely rewarding even on a changeable day, fit visitors facing few real problems regardless of forecast. Regulars recommend checking Met Eireann for current conditions rather than trusting a seasonal average. Posters describe wrapping up properly as the real key to enjoying outdoor activity, cold snaps entirely possible even on an otherwise mild week. Regulars call the park worth visiting in any weather, the lakes and mountains striking regardless of cloud cover. The record: 10.4C days feeling like 7C, 4.3C nights, an extraordinarily high 115.6mm across nearly 17 days and 84 percent humidity.
KillarneyMarchRegular · March · 1 month ago · Read more on Tripadvisor ↗
Killarney-forum threads on an April 13th visit call this timing entirely reasonable, posters describing mid-April as genuinely warming up compared with earlier in the month. Regulars call the window between Easter and the May bank holiday a real sweet spot, everything open and running but crowds still considerably lighter than peak summer. Posters describe Irish weather in April as capable of anything, clear and sunny one day, properly wet and windy the next, occasionally even a cold snap with a touch of snow. Regulars call late April a genuinely better bet than March, both weather and buzz noticeably improved by then. Posters recommend real waterproof layers regardless of how settled the forecast looks. Regulars call the national park worth visiting in any April weather, cycling and walking routes both genuinely rewarding. The record: 12.8C days feeling like 10C, 6.1C nights, 85mm across over 13 days and 80 percent humidity.
KillarneyAprilRegular · April · 1 month ago · Read more on Tripadvisor ↗
Killarney-forum threads on a February visit are direct real unsettled weather is the safer assumption, posters calling this genuinely hard to predict, capable of turning sunny and calm or damp and dark with little warning. Regulars call accommodation prices a real upside of the off-season timing, considerably cheaper than the summer peak. Posters describe a lucky clear February day as genuinely rewarding, the bare mountainsides and leafless trees opening up views that summer's foliage blocks. Regulars call a passing shower typically brief on the Ring of Kerry, the usual pattern running shower-clear-shower rather than an all-day soak. Posters recommend real waterproof layers regardless of how the morning starts. Regulars call the national park worth visiting in any February weather. The record: 9.4C days feeling like 6C, 4.6C nights, a notably high 122.7mm across nearly 17 days and 85 percent humidity.
KillarneyFebruaryRegular · February · 1 month ago · Read more on Tripadvisor ↗
May is one of the two months Killarney regulars name first - May and September, ahead of the July and August crush - and their case joins weather to space: the countryside at its best, sites that are not crowded, and rates below high season. Reports of late May run 60 to 70F with very little rain, with a single all-day wet day in a fortnight described as ordinary rather than lucky. One date to route around: the first weekend of May is a bank holiday, and Killarney hosts the Rally of the Lakes then, which takes over the town and the roads unless the rally is why you came. The record: 15.9C days that feel like 14C, 8.9C nights, 12.4 precipitation days carrying 76.9mm, 10.8 hours of sun and a 15.7-hour day.
RallyOfTheLakesWeekend · May · 1 month ago · Read more on Tripadvisor ↗

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Killarney climate normals — September

Daytime high17°C / 62°F🙂 cool
Nighttime low11°C / 52°F
Feels like (high)15°C / 59°F
Sea temperature18°C / 64°F🧊 bracing
Rainfall107 mm / 4.2 in🌧 rainy
Rainy days15 days
Humidity85%💦 very humid
Dew point11°C / 52°F
Sunshine7.5 h/day
Daylight12.6 h
Wind19 km/h / 12 mph
Air quality (US AQI)34🍃 good

Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.

Crowds in Killarney 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)

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Peak crowdsBusyShoulder seasonQuiet

Best months for Killarney'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 weatherKillarney's weather peaks May–July.

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Best weatherFair weatherToughest weather

What's on in Killarney in September

Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.

  • Nature

    Red deer rut

    25 Sep – 25 Oct · usuallyRutting season

    The native herd in the national park is the last wild one in Ireland, and through October the stags roar across Knockreer and the Muckross oakwoods. Keep well back; they are not tame.

What's on around the world in September →

Nearby, and something's on

Within 300 km of Killarney — a day trip or a short hop — with something on this month. Never part of the comfort score.

Where is Killarney?

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Killarney in September — FAQ

Is September a good time to visit Killarney?
September in Killarney: cool, rainy, with clean air — an excellent time to visit. It ranks #6 of 12 months for Killarney on SeasonMap's comfort score (81/100).
What is the weather like in Killarney in September?
In September, Killarney averages a daily high of 16.7°C and a low of 11.2°C, with about 107.4 mm of rain over roughly 15.2 rainy days.
What is the air quality in Killarney in September?
Killarney has a mean US Air Quality Index of about 34 in September.

Within 300 km: Dingle's Blasket Islands boats around 1 Apr – 30 Sep, and Dublin's Culture Night around 15–25 Sep.