Viana do Castelo weather in August
Temperature, sea and sunshine in August: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in August
Good
Best time to visit: July – August
What is the weather like in Viana do Castelo in August?
In August, Viana do Castelo is warm: daytime highs average 23 °C, and nights cool down to about 17 °C. The sea averages 17.2 °C – bracing, so a wetsuit helps for longer swims. With around 10 hours of sunshine a day, there is plenty of sun. Rain is rare: about 4 days bring 26 mm in total. All in all, August is a good month for a holiday in Viana do Castelo.
August compared
How the weather changes from July to September. Tap a month to open it.
| JulyJul | AugustAug | SeptemberSep | |
|---|---|---|---|
| Score | 60 | 63 | 47 |
| Day | 23° | 23° | 22° |
| Night | 17° | 17° | 16° |
| Sea | 17° | 17° | 17° |
| Sun | 10 h | 10 h | 8 h |
| Rain days | 4 | 4 | 7 |
More details for August
- Daylight
- 13 h 54 min06:43 – 20:37
- UV index
- 8 · very highclear sky, noon (estimate)All months
- Muggy days
- 2 daysdew point 18 °C or moreAll months
- Wind
- 20 km/haverage daily peakAll months
- Cloud cover
- 34 %on averageAll months
- Hot days
- 0 days30 °C or more
- Time zone
- UTC+1Europe/Lisbon
How the score comes together
- Temperatureweight 35 %63 %
- Seaweight 25 %3 %
- Sunshineweight 20 %100 %
- Few rainy daysweight 20 %100 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in August
- Wetsuit for longer swims
- Sunscreen
- Sunglasses & sun hat
Viana do Castelo in August: quick answers
Is Viana do Castelo hot in August?
Warm rather than hot: in August, daytime highs in Viana do Castelo average 23 °C and nights cool to about 17 °C.
Can you swim in Viana do Castelo in August?
Only if you don't mind cold water: in August 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 August?
Rain is rare: about 4 days bring 26 mm in total.
Viana do Castelo month by month
The whole year in Viana do CasteloAll destinations: PortugalWhere to go in AugustSea temperature in August
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