Sesimbra seasonal overview
Best Surf Season (October - March)
The Portuguese Atlantic ratchets up quickly in October and stays energized through March. Climatologically, the Icelandic Low deepens and a parade of extratropical cyclones roll across the North Atlantic, sending long-period, powerful swell toward Iberia. At Sesimbra, the SSW-facing bay is perfectly positioned to catch south and southwest quadrant swells, while the frequent N/NNE/NNW winds blow offshore or cross-offshore and keep the faces clean. Average surf heights sit in the 5-7ft (1.5-2.1m) range and periods regularly exceed 12s. Depending on the NAO, some winters stack up more WNW/NW groundswell while others deliver extra SW systems, but either way the bay is firmly in play from October through March. This is the window when the bay gets proper groundswell, especially when the Azores High builds ahead of a cold front and the wind swings offshore.
Fair Surf Season (April - May & September)
Spring and early autumn are transitional. The North Atlantic is less active, but every few days a low-pressure system still pushes a solid W/NW swell through. Average heights drop to 3-5ft (0.9-1.5m) with periods around 10-11s. The wind is still predominantly N/NE and offshore enough to groom the waves. True SSW/SW swells are rare, yet when they appear they can light Sesimbra up in excellent shape. These months are best for scoring fun, rippable waves without the heavier North Atlantic storm energy.
Low Surf Season (June - August)
Summer is the quietest stretch. The Azores High ridges in over Iberia, the storm track shifts north, and the bay is left with mostly small NW/WNW windswell. Average surf heights hover around 3-4ft (0.9-1.2m) with periods in the 8-9s range. N/NNW winds still blow reliably, which keeps the surface clean, but the lack of period and overhead size makes it a groveling, small-wave season. A rare south-southwest groundswell can break the boredom, but generally expect fun, mellow summer surf rather than heavy Atlantic juice.