Dundalk weather in September

In September, Dundalk sees average daytime highs of 16°C and overnight lows near 10°C, with 67 mm of rain across 12.1 wet days and about 12.5 hours of daylight. It is the 4th-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 17°C in the first days to 15°C by the end. The sky is clear or mostly clear about 7% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 30 min at the start of September to 11 h 24 min by month's end. Set against the rest of the year, September is Dundalk's 9th-clearest and 8th-windiest month. For the whole year in context, see Dundalk's year-round climate.

Daytime high
16°
4th warmest
Overnight low
10°
9th coldest
Rainfall
67 mm
12.1 wet days
Daylight
12 h 24 min
6:07 AM – 6:33 PM
Cloud cover
78%
9th clearest
Wind
14 km/h
8th windiest
Solar energy
2.64 kWh/m²
Travel score
4.5
out of 10

Dundalk is county town and administrative capital of County Louth, Ireland.

Air quality
Excellent
PM10 14.4 µg/m³ · 2019
Density
1,747/km²
people per km²
Founded
~3499 BCE

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 17°C in the first days to 15°C by the end.

A typical September day in Dundalk reaches about 16°C in the afternoon and slips back to 10°C overnight — a 6°C spread between the day's warmth and the night's chill. On most days the high lands between 14°C and 19°C. Set against its neighbours, September runs about 2°C cooler than August and about 3°C warmer than October.

10°15°20°151015202530
Avg high (°C)Avg low (°C)
11711
21711
31711
41711
51711
61711
71711
81711
91711
101710
111710
121610
131610
141610
151610
161610
171610
181610
191610
201610
211610
22169
23159
24159
25159
26159
27159
28159
29159
30159

How September really feels in Dundalk

Once humidity and wind are folded in, September averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Dundalk weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / 7113.31.17.70.9
Feb / 5811.919.41.1
Mar / 6012.60.711.51.8
Apr12° / 6512.60.113.72.7
May14° / 6913.8015.73.7
Jun17° / 10°7513016.84.7
Jul18° / 12°7614.5016.35.1
Aug18° / 12°8313.7014.65.1
Sep16° / 10°6712.1012.54.5
Oct13° / 7812.4010.23.2
Nov10° / 8113.30.18.31.9
Dec / 7512.30.77.21.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 7% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 13% of September, with mostly cloudy or overcast conditions the remaining 80%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
11981
22080
32080
41981
51981
61981
71981
81981
91981
101981
112080
122179
132179
142179
152080
162179
172179
182179
192179
202179
212179
222179
232179
242179
252179
262080
272080
282080
292179
302179

Chance of precipitation in September

Any precipitation

Dundalk gets around 67 mm of rain over 12.1 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 39% and peaks near 42% on the wettest days.

0%10%20%30%40%50%151015202530
Rain chance (%)
137
237
338
438
539
639
739
840
940
1040
1140
1240
1340
1439
1539
1639
1738
1838
1938
2038
2138
2239
2339
2440
2541
2641
2742
2842
2942
3042

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the dry band about 85% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
178202
278202
378202
478193
578193
679183
780182
881172
982162
1082162
1183152
1284142
1385141
1486131
1586131
1687121
1788120
1888120
1989110
2089110
2189110
2289110
2389110
2490100
2590100
2690100
2790100
289190
299190
309190

Wind in September

Winds average 14 km/h in September.

Across September, daily wind ranges from about 14 km/h on the calmest days to 15 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202530
Wind speed (km/h)Feels
114light breeze
214light breeze
314light breeze
414light breeze
514light breeze
614light breeze
714light breeze
814light breeze
914light breeze
1014light breeze
1114light breeze
1214light breeze
1314light breeze
1414light breeze
1514light breeze
1614light breeze
1714light breeze
1814light breeze
1914light breeze
2014light breeze
2114light breeze
2214light breeze
2314light breeze
2414light breeze
2514light breeze
2614light breeze
2715light breeze
2815light breeze
2915light breeze
3015light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 30 min at the start of September to 11 h 24 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 126 minutes over September. Sunrise moves from 5:40 AM to 6:33 AM, and sunset from 7:11 PM to 5:57 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.55:407:11
213.55:417:09
313.45:437:06
413.35:457:04
513.25:477:01
613.25:496:58
713.15:516:56
813.05:526:53
912.95:546:51
1012.95:566:48
1112.85:586:46
1212.76:006:43
1312.66:026:41
1412.66:046:38
1512.56:056:35
1612.46:076:33
1712.46:096:30
1812.36:116:28
1912.26:136:25
2012.16:156:22
2112.16:166:20
2212.06:186:17
2311.96:206:15
2411.86:226:12
2511.86:246:09
2611.76:266:07
2711.66:286:04
2811.56:306:02
2911.56:315:59
3011.46:335:57

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 2.64 kWh/m².

For context, solar energy here swings from a low near 0.49 kWh/m² to a high of 4.81 kWh/m² in May across the year — September's 2.64 kWh/m² falls in the middle.

01234151015202530
Solar energy (kWh/m²)Level
13.2Moderate
23.1Moderate
33.1Moderate
43.1Moderate
53.0Moderate
63.0Moderate
73.0Moderate
82.9Moderate
92.9Moderate
102.9Moderate
112.8Moderate
122.8Moderate
132.8Moderate
142.7Moderate
152.7Moderate
162.7Moderate
172.6Moderate
182.6Moderate
192.5Moderate
202.5Moderate
212.5Moderate
222.4Moderate
232.4Moderate
242.4Moderate
252.3Moderate
262.3Moderate
272.2Moderate
282.2Moderate
292.1Moderate
302.1Moderate
Planning a trip in September

Is September a good time to visit Dundalk?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

4.5
Sightseeing
4th-best month of the year
0.6
Beach & pool
4th-best month of the year

September is a reasonable time to visit Dundalk for sightseeing.

What to pack for Dundalk in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, Dundalk sees daytime highs around 16°C and nights near 10°C. Worth packing: a warm layer and rain gear. About 12 days see rain.

a warm layerrain gear

Sea temperature near Dundalk in September

The nearest coast averages about 14°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 14 km away) is warmest in August at about 15°C and coldest in March near 8°C.

The water stays below 20°C all year — cool enough that most swimmers want a wetsuit.

5°10°15°JanFebMarAprMayJunJulAugSepOctNovDecbracingcool
Sea temperature (°C)Comfort
Jan9Bracing
Feb8Bracing
Mar8Bracing
Apr9Bracing
May11Bracing
Jun13Bracing
Jul15Bracing
Aug15Cool
Sep14Bracing
Oct13Bracing
Nov12Bracing
Dec10Bracing

UV index in Dundalk in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Dundalk peaks around August 10 at about 5 (high) — a little sun protection helps at midday. It bottoms out near December 20 at about 0 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 6 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighModerateLowAug 10UV 5Dec 20UV 0
UV index (midday)Level
Jan1Low
Feb1Low
Mar2Moderate
Apr3Moderate
May5High
Jun5High
Jul5High
Aug5High
Sep4Moderate
Oct2Low
Nov1Low
Dec0Low
Location & terrain

Where is Dundalk?

Dundalk sits at 54.0°N, 6.4°W, 18 m above sea level, in Ireland. The nearest listed city is Newry, 21 km away.

DroghedaBanbridgeNavanBalbrigganPortadownCraigavonSwords

Topography around Dundalk

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Dundalk.

Within 3 km, the terrain around Dundalk has only modest variations in elevation — a maximum elevation change of 58 m around an average of 18 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 582 m; within 80 km, large variations in elevation — a maximum elevation change of 852 m.

The land around Dundalk is covered by grassland (51%) and artificial surfaces (21%) within 3 km, grassland (57%) within 16 km, and grassland (62%) and water (24%) within 80 km.

3 km
58 m
16 km
582 m
80 km
852 m
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Newry 21 km · Drogheda 32 km · Banbridge 40 km · Navan 42 km · Balbriggan 46 km · Portadown 47 km · Craigavon 50 km · Swords 61 km

Ireland travel facts

Travel advisory
Level 1
Exercise Normal Precautions
Power plugs
Type G
230 V · 50 Hz
Prices
≈ 85% of US
price level, 2025
GDP per capita
$131,592
2025
Happiness
6.9 / 10
World Happiness, 2025
Safe drinking water
96%
of population, 2024
Homicide rate
0.7
per 100k, 2023
Road deaths
3.1
per 100k/yr, 2019
Income group
High
World Bank
Religion
Roman Catholic 69%none 15%Protestant 4%Orthodox 2%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Dundalk (54°, -6.4167°, elevation 18 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).