Cardiff Weather in September

September in Cardiff brings pleasant temperatures, with highs of 18°C (64°F) and nights dropping to 12°C (54°F). Rainfall is on the higher side this month, averaging around 90 mm (3.5 in), so keep a rain jacket handy.

Rainfall in Cardiff in September

Rain is expected on roughly 16 days, totalling around 90 mm (3.5 in) for the month. Expect a fairly normal spread of rainfall this month, with no particular pattern of very heavy or very persistent showers.

Temperature in Cardiff in September

If you're visiting Cardiff in September, expect highs of 18°C (64°F) and overnight lows around 12°C (54°F). September is typically considered a summer month. Even when the weather is stable, mornings and evenings can still feel distinctly cool. At 12°C (54°F) overnight, it can feel quite a bit cooler after dark. Worth packing something warmer for evenings, but the cooler temperatures are ideal for sleeping.

Sunshine in Cardiff in September

The city usually sees around 149 hours of sunlight, indicating a moderately sunny period.

Wind Speed in Cardiff in September

Wind speeds average 4 m/s (8 knots) during September. At this speed, expect moderate winds that can raise dust and move small branches. Since this is an average, some days have gentle light winds while others experience stronger breezes that are quite noticeable.

Average water temperature in September

The water temperature is 15°C (59°F) — chilly, but perfectly fine for a swim if you're not too sensitive to cold water. A short wetsuit can make longer sessions more comfortable.

Our weather planner can help you find worldwide destinations with pleasant weather during this period. July and August typically offer the best weather for Cardiff.

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

Cardiff Temperature in September

Min Temperature 12°C (54°F)  

Max Temperature 18°C (64°F)  

Water Temperature 15°C (59°F)  

Chance of Rain 52%  

Precipitation 90 mm (3.5 in)  

Rainy days 16 days  

Humidity 81%  

Windspeed 4 m/s (8 knots)  

Sunshine 149 hours  

Percentage Sunshine 37%  

Daily Historical Temperatures

50-year average (1976-2025)

Based on our historical records, temperatures in Cardiff typically stay consistent throughout September, with daily highs averaging around 18°C (64°F). Nights are cool, with lows typically ranging from 10°C (50°F) to 12°C (54°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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Historical weather for Cardiff in September

Browse day-by-day weather records for Cardiff 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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Cardiff historical weather extremes in September

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

• The hottest September day on record in Cardiff reached 28°C (82°F) (September 4, 2023).
• Cardiff experienced its chilliest September day on September 15, 1986, reaching only 11°C (52°F).
• Nighttime temperatures dropped to 2°C (36°F) on September 30, 1988, marking the coldest September night on record.
• The wettest day in September Cardiff was on September 24, 2012 with 32 mm (1.3 in) of precipitation.

What to Wear in Cardiff 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. Sunglasses could come in handy during the sunnier parts of your trip.

What To Do in Cardiff in September

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

Swimming

6/10

Cycling

9/10

Walking

9/10

Camping

8/10

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 the United Kingdom, check out our Cardiff's climate page.

More climate data for Cardiff

Temperature Rainfall Sunshine Humidity Wind Speed Water Temp

See the full Cardiff climate overview or explore weather in the United Kingdom.