Viana do Castelo 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
Fair
Best time to visit: July – August
What is the weather like in Viana do Castelo in September?
In September, Viana do Castelo is warm: daytime highs average 22 °C, and nights cool down to about 16 °C. The sea averages 17.2 °C – bracing, so a wetsuit helps for longer swims. The sun shines for around 8 hours a day. Rain falls on about 7 days, adding up to 71 mm. All in all, September is a so-so month for a holiday in Viana do Castelo.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 63 | 47 | 15 |
| Day | 23° | 22° | 19° |
| Night | 17° | 16° | 14° |
| Sea | 17° | 17° | 17° |
| Sun | 10 h | 8 h | 5 h |
| Rain days | 4 | 7 | 13 |
More details for September
- Daylight
- 12 h 33 min07:14 – 19:47
- UV index
- 6 · highclear sky, noon (estimate)All months
- Muggy days
- 1 daydew point 18 °C or moreAll months
- Wind
- 18 km/haverage daily peakAll months
- Cloud cover
- 45 %on averageAll months
- Hot days
- 0 days30 °C or more
- Time zone
- UTC+1Europe/Lisbon
How the score comes together
- Temperatureweight 35 %42 %
- Seaweight 25 %3 %
- Sunshineweight 20 %82 %
- Few rainy daysweight 20 %79 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in September
- Wetsuit for longer swims
- Sunscreen
- A jumper for the evenings
Viana do Castelo in September: quick answers
Is Viana do Castelo hot in September?
Warm rather than hot: in September, daytime highs in Viana do Castelo average 22 °C and nights cool to about 16 °C.
Can you swim in Viana do Castelo in September?
Only if you don't mind cold water: in September the sea averages just 17.2 °C. Comfortable swimming temperatures are not reached at any time of year.
Does it rain much in Viana do Castelo in September?
Rain falls on about 7 days, adding up to 71 mm.
Viana do Castelo month by month
The whole year in Viana do CasteloAll destinations: PortugalWhere 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