Derry weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Poor
Best time to visit: April – June
What is the weather like in Derry in September?
In September, Derry is cool: daytime highs average 16 °C, and nights cool down to about 11 °C. The sea averages 14.6 °C – swimming is only for the hardy. The sun is scarce, with only about 4 hours a day. It rains often – on about 15 days, adding up to 78 mm. All in all, September is not an ideal month for a holiday in Derry.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 7 | 6 | 1 |
| Day | 17° | 16° | 13° |
| Night | 12° | 11° | 8° |
| Sea | 15° | 15° | 13° |
| Sun | 5 h | 4 h | 3 h |
| Rain days | 17 | 15 | 17 |
More details for September
- Daylight
- 12 h 50 min07:00 – 19:50
- UV index
- 3 · moderateclear sky, noon (estimate)All months
- Muggy days
- 0 daysdew point 18 °C or moreAll months
- Wind
- 26 km/haverage daily peakAll months
- Cloud cover
- 77 %on averageAll months
- Hot days
- 0 days30 °C or more
- Snow days
- 0 days1 cm or more of fresh snow
- Time zone
- UTC+1Europe/London
How the score comes together
- Temperatureweight 35 %0 %
- Seaweight 25 %0 %
- Sunshineweight 20 %12 %
- Few rainy daysweight 20 %21 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in September
- Sunscreen
- A jumper for the evenings
- Rain jacket or umbrella
Derry in September: quick answers
Is Derry hot in September?
No. In September, Derry is cool: daytime highs average 16 °C and nights drop to about 11 °C.
Can you swim in Derry in September?
Only if you don't mind cold water: in September the sea averages just 14.6 °C. Comfortable swimming temperatures are not reached at any time of year.
Does it rain much in Derry in September?
It rains often – on about 15 days, adding up to 78 mm.
Derry month by month
The whole year in DerryAll destinations: United KingdomWhere to go in SeptemberSea temperature in September
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences