Waterville Weather in September

September in Waterville brings moderate temperatures, with daytime highs of 17°C (63°F) and nights around 12°C (54°F). Quite a bit of rainfall is expected, around 116 mm (4.6 in), so pack an umbrella.

Rainfall in Waterville in September

You can expect rain on around 20 days based on historical patterns, with 116 mm (4.6 in) average for the month. Wet weather is a regular and significant part of this month. Frequent days of rain combined with high totals means proper waterproofs are worth packing.

Temperature in Waterville in September

In September, Waterville gets moderate temperatures, with highs of 17°C (63°F). Nights cool to around 12°C (54°F). Conditions are often most pleasant around the middle of the day. Nights cool down to 12°C (54°F), so a light jacket or extra layer is useful once the sun goes down. On the plus side, the cooler nights make for comfortable sleeping conditions.

Sunshine in Waterville in September

The city usually sees around 118 hours of sunlight, indicating a moderately sunny period.

Wind Speed in Waterville in September

Wind speeds average 5 m/s (10 knots) during September. At this speed, gentle to moderate breezes make small trees sway and the wind creates whitecaps on water bodies. Daily variations range from moderate winds to stronger breezes, creating excellent conditions for sailing, kite flying and wind sports.

Average water temperature in September

At 15°C (59°F), the water is cool but manageable for those who don't mind a bit of a shock getting in. Most people adjust after a few minutes.

If you prefer dry days with pleasant temperatures, May, June, July and August typically offer 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.

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For a detailed overview over the year and the best time to visit Ireland, check out our Waterville's climate page.

Waterville Temperature in September

Min Temperature 12°C (54°F)  

Max Temperature 17°C (63°F)  

Water Temperature 15°C (59°F) *  

Chance of Rain 67%  

Precipitation 116 mm (4.6 in)  

Rainy days 20 days  

Humidity 77% *  

Windspeed 5 m/s (10 knots) *  

Sunshine 118 hours *  

Percentage Sunshine 30% *  

* Data from: Valentia, Ireland (12 KM, 7 Miles).

Daily Historical Temperatures

50-year average (1976-2025)

Based on our historical records, temperatures in Waterville typically stay consistent throughout September, with daily highs averaging around 17°C (63°F). Nights are cool, with lows typically ranging from 11°C (52°F) to 13°C (55°F).

Average temperatures in September

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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

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‹ January February March April May June July August September October November December ›

Historical weather for Waterville in September

Browse day-by-day weather records for Waterville spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.

Historical weather Temperatures Precipitation

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‹ January February March April May June July August September October November December ›

Waterville historical weather extremes in September

Based on 49 years of weather observations (1976-2025), these are the most extreme conditions recorded in Waterville.

• On September 5, 1991, temperatures climbed to 28°C (82°F), marking the warmest September day on record.
• The coldest September day was on September 20, 2018, with a maximum of 12°C (54°F).
• Waterville registered its coldest September night on September 26, 1992, with temperatures dropping to 3°C (37°F).

What to Wear in Waterville in September

Comfortable temperatures call for an easy wardrobe in September. Pack summer basics like t-shirts and shorts, but include a light jacket for cooler moments. A pair of comfortable walking shoes is essential. Expect heavy rainfall, so bring good rain protection and waterproof bags. With water temperatures around 15°C (59°F), the water is quite cold for swimming. You can skip the swimwear unless you're particularly tough. Bring sunglasses since you'll have some sunny periods throughout the month

What To Do in Waterville in September

We rated the following activities from 1 (least suitable) to 10 (best) to do.

Swimming

6/10

Cycling

5/10

Walking

5/10

Camping

6/10

Outdoor sports

9/10

Select a Month

Check the conditions for any month of the year.

• January
• February
• March
• April

• May
• June
• July
• August

• September
• October
• November
• December

For a detailed overview over the year and the best time to visit Ireland, check out our Waterville's climate page.

More climate data for Waterville

Temperature Rainfall Sunshine Humidity Wind Speed Water Temp

See the full Waterville climate overview or explore weather in Ireland.