Castlebar Weather in September
September in Castlebar brings moderate temperatures around 17°C (63°F) during the day, dropping to 10°C (50°F) at night, with quite a bit of rainfall expected, averaging around 94 mm (3.7 in) for the month.
Rainfall in Castlebar in September
Historically, September sees about 21 days of rain, with a monthly average of 94 mm (3.7 in). This is a month with many wet days but modest rainfall totals, so showers are generally light and easy to manage.
Temperature in Castlebar in September
In September, Castlebar sees moderate temperatures, with highs of 17°C (63°F). Nights drop to around 10°C (50°F). This creates a mild day-to-night pattern that is generally easy to manage with the right clothing. Nights drop to around 10°C (50°F), which is noticeably cooler than the daytime. A light jacket for the evening is a sensible addition, and the cool nights tend to make sleeping comfortable.
Sunshine in Castlebar in September
The city usually sees around 93 hours of sunlight, indicating fewer sunny days.For Castlebar itself, June generally stands out with the best circumstances. If you're seeking pleasant, dry and sunny weather somewhere else in the world, our weather planner can help you explore other options.
Castlebar Temperature in September
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Castlebar Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Castlebar - and find the best time to visit.
Daily Historical Temperatures
50-year average (1976-2025)
Based on our historical records, temperatures in Castlebar typically stay consistent throughout September, with daily highs averaging around 17°C (63°F). Nights are cool, with lows typically ranging from 9°C (48°F) to 11°C (52°F).
Average temperatures in September
Daily Historical Precipitation
50-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in September
Historical weather records for Castlebar in September
Browse day-by-day weather records for Castlebar spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
Castlebar historical weather extremes in September
According to our 49 years of weather records for Castlebar, the following extremes were recorded between 1976 and 2025.
- On September 7, 2023, temperatures climbed to 26°C (79°F), marking the warmest September day on record.
- The coldest September day was on September 26, 2024, with a maximum of 10°C (50°F).
- The lowest overnight temperature recorded in September was 1°C (34°F) (September 5, 1992).
Best Places in Ireland in September
Find out more about the weather in Ireland and which places have the best travel conditions in this month. See all of Ireland in September →
Perfect weather is subjective. On this map perfect weather has been defined with temperatures between 20°C (68°F) and 29°C (84°F) and not too much precipitation (less than 90 mm (3.5 in) a month).
What to Wear in Castlebar in September
Pleasant temperatures in September mean you can pack light but flexibel pieces. Think cotton t-shirts, comfortable walking shorts, and one warmer layer for evenings. A light sweater or denim jacket works well. Prepare for significant rainfall with proper waterproof clothing and shoes. You can probably leave your sunglasses at home, because sunny days are pretty rare this month.
What To Do in Castlebar in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
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Swimming4/10 -
Cycling6/10 -
Walking6/10 -
Camping8/10 -
Outdoor sports9/10
Castlebar 3-Day Forecast
Temperature Rainfall Sunshine Humidity
See the full Castlebar climate overview or explore weather in Ireland.
Popular in September
Where to go in September - average daytime high across popular destinations.
Westport
17°C (63°F) Doolin17°C (63°F) Kilkenny
18°C (64°F) Cork18°C (64°F) Kenmare18°C (64°F) Killarney17°C (63°F) Galway18°C (64°F) Dublin18°C (64°F) 
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