#1 in September
24.1°C
NOAA Season Curve (May–Oct):
M
19.8°
J
21.4°
J
22.8°
A
23.9°
S
24.1°
O
23.2°
N
21.2°
NOAA SATELLITE DATA (1991–2020 30-YEAR CLIMATOLOGY)
PTPortugal Sea Temperature in September
Historical 30-year sea surface temperatures across 44 coastlines in Portugal for September. Derived from NOAA 0.25° blended satellite and in-situ marine observations.
Climatology Notice: Temperatures represent the 30-year long-term historical average (1991–2020 normal), not a live single-day sensor forecast.
Bathing Climatology Gauge · Portugal (September)
NOAA OISST v2.1 (0.25° Marine Grid)
20.5°C
Refreshing / Invigorating
Mean sea surface temperature across 44 monitored coastlines
Swimmability Verdict
Refreshing & Invigorating Plunge
Warmest Coastline
24.1°C
Coldest Surveyed Shore
17.4°C
Swimmable Ratio (≥21°C)
36% of coastlines16/44
While national waters average below 21°C, 16 of 44 coastlines clear the swim threshold in July. Focus your trip on sheltered south-facing coves and shallow bays.
Plan Your September Trip to Portugal
Autumn shoulder-season rates are currently live across Portugal. Pair warm coastal waters with discounted stays and uncrowded beaches.
Warmest Swimming Bases in Portugal (September)
The top 3 coastlines holding highest water temperatures based on 30-year NOAA climatology.
Select Month
View 12-Month Annual Overview →Canary Current, Coastal Upwelling & The Nazaré Canyon
Despite sitting at Mediterranean latitudes, Portugal’s Atlantic coast and Algarve exhibit cool sea surface temperatures (averaging 18.5–20.3°C in August). Persistent northerly summer winds (the Nortada) push surface waters offshore, driving active coastal upwelling that draws deep, nutrient-rich ocean layers (14–16°C) to the shoreline. Off central Portugal at Nazaré, the continental shelf is bisected by the Nazaré Submarine Canyon (Canhão da Nazaré), a 230km long, 5,000m deep underwater chasm terminating just 1km offshore. In winter, this bathymetric trench acts as a hydraulic funnel, refracting and focusing North Atlantic storm swells into world-record 20–30m breaking waves at Praia do Norte.
Oceanographic Phenomenon:Summer Upwelling (Nortada) & Deep Canyon Wave Refraction
Thermal Lag Characteristic:Pronounced oceanic thermal lag: Atlantic water temperature peaks in late August and September (20.3°C), warming far slower than Mediterranean basins but buffering autumn cooling.
Peak Bathing Average:August / September
The September Thermal Lag Advantage
Because seawater has a high specific heat capacity, it acts as a massive thermal battery. Southern European and Mediterranean basins absorb solar energy all summer, reaching maximum heat storage by late August. In September, while air temperatures drop, the water releases heat slowly, which creates sea temperatures that are typically 3°C to 5°C warmer than in June.
CYPRUS (AYIA NAPA / PROTARAS)
27.5°C
Effortless swimming
TURKEY (ANTALYA / KAŞ)
27.3°C
Warm bathwater
GREECE (CRETE / RHODES)
25.4°C
Extended season
MALTA & GOZO
26.1°C
Crystal clear
Portugal Beaches in September
Individual coordinate lookups from NOAA 0.25° marine grid.
Showing 44 coastlines
Explore Sea Temperatures by Country
Spain(23.7°C)Italy(25.9°C)Turkey(27.3°C)France(22.4°C)Greece(25.4°C)Cyprus(27.7°C)Croatia(25.2°C)Albania(25.5°C)Montenegro(25.7°C)Malta(26.7°C)Bulgaria(25.1°C)Romania(24.7°C)Slovenia(25.4°C)Portugal(20.7°C)Poland(19°C)Sweden(18.3°C)Netherlands(18.5°C)Bosnia & Herzegovina(25.2°C)Monaco(24.6°C)Latvia(18.5°C)Estonia(18°C)Lithuania(18.8°C)Germany(18.6°C)Denmark(18°C)Norway(15.3°C)Belgium(18.7°C)Faroe Islands(10.9°C)United Kingdom(16.1°C)Ireland(15.9°C)Iceland(10.9°C)Finland(16.6°C)
