Cascais 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
Good
Best time to visit: June – September
What is the weather like in Cascais in September?
In September, Cascais is warm: daytime highs average 25 °C, and nights cool down to about 18 °C. The sea averages 18.8 °C – bracing, so a wetsuit helps for longer swims. The sun shines for around 8 hours a day. Rain is rare: about 4 days bring 31 mm in total. All in all, September is a good month for a holiday in Cascais.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 81 | 76 | 44 |
| Day | 26° | 25° | 22° |
| Night | 19° | 18° | 16° |
| Sea | 19° | 19° | 19° |
| Sun | 10 h | 8 h | 6 h |
| Rain days | 1 | 4 | 9 |
More details for September
- Daylight
- 12 h 30 min07:18 – 19:48
- UV index
- 7 · highclear sky, noon (estimate)All months
- Muggy days
- 3 daysdew point 18 °C or more
- Wind
- 21 km/haverage daily peak
- Cloud cover
- 36 %on average
- Hot days
- 1 day30 °C or more
- Time zone
- UTC+1Europe/Lisbon
How the score comes together
- Temperatureweight 35 %92 %
- Seaweight 25 %26 %
- Sunshineweight 20 %88 %
- Few rainy daysweight 20 %97 %
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
- Sunglasses & sun hat
Cascais in September: quick answers
Is Cascais hot in September?
Warm rather than hot: in September, daytime highs in Cascais average 25 °C and nights cool to about 18 °C. On about 1 days the thermometer climbs to 30 °C or more.
Can you swim in Cascais in September?
Only if you don't mind cold water: in September the sea averages just 18.8 °C. Comfortable swimming temperatures are not reached at any time of year.
Does it rain much in Cascais in September?
Rain is rare: about 4 days bring 31 mm in total.
Cascais month by month
The whole year in CascaisAll 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)