Ocean temperatures are often below 20°C (68°F) so wearing a wetsuit is oftentimes necessary. You’ll need 3/2 mm wetsuit for summer and 4/3 mm wetsuit for winter. Approximate ocean temperatures in Portugal are 15-18°C (59-64.5°F) in spring, 18-21°C (64.5-70°F) in summer, 16-18°C (61-64.5°F) in fall, and 13-15°C (55-59°F) in winter.
Air temperatures are mostly above 20°C (68°F) from May through October, and they’re mainly above 30°C (86°F) during summer months.