Cascais has a warm-summer Mediterranean climate (Köppen Csb) moderated by the Atlantic Ocean. Temperatures stay mild year-round: the average high ranges from 15°C (59°F) in January to 26°C (79°F) in July and August. The town gets roughly 535mm of rain annually, almost all of it falling between October and April. Summers are dry with 10-12 hours of daily sunshine, while winters bring short bursts of rain between long sunny spells. The ocean stays cool even in summer: sea temperatures peak at 19°C (66°F) in August and September and dip to 14°C (57°F) in February. See the where to stay guide for more details.
Cascais Weather by Month: Temperature, Rainfall, and Sunshine
The table below shows average daily highs, lows, rainfall, sea temperature, and sunshine hours for each month. See the travel tips and FAQ guide for more details.
| Month | Avg High | Avg Low | Rainfall (mm) | Sea Temp | Sun (hrs/day) |
|---|---|---|---|---|---|
| Jan | 15°C / 59°F | 9°C / 48°F | 100 | 15°C / 59°F | 5 |
| Feb | 16°C / 61°F | 9°C / 48°F | 85 | 14°C / 57°F | 6 |
| Mar | 18°C / 64°F | 11°C / 52°F | 55 | 15°C / 59°F | 7 |
| Apr | 19°C / 66°F | 12°C / 54°F | 65 | 15°C / 59°F | 8 |
| May | 21°C / 70°F | 14°C / 57°F | 45 | 17°C / 63°F | 10 |
| Jun | 24°C / 75°F | 16°C / 61°F | 15 | 18°C / 64°F | 11 |
| Jul | 26°C / 79°F | 18°C / 64°F | 5 | 19°C / 66°F | 12 |
| Aug | 26°C / 79°F | 18°C / 64°F | 5 | 19°C / 66°F | 11 |
| Sep | 25°C / 77°F | 17°C / 63°F | 25 | 19°C / 66°F | 9 |
| Oct | 22°C / 72°F | 15°C / 59°F | 75 | 18°C / 64°F | 7 |
| Nov | 18°C / 64°F | 12°C / 54°F | 110 | 17°C / 63°F | 5 |
| Dec | 15°C / 59°F | 10°C / 50°F | 115 | 16°C / 61°F | 5 |
Cascais Weather in Spring (March to May)
Spring warms up quickly in Cascais. March still feels cool with highs around 18°C (64°F) and some rain (55mm over about 7 wet days), but by May daily highs reach 21°C (70°F) and rain drops to 45mm. Sunshine climbs from 7 hours a day in March to 10 in May. The sea stays chilly at 15-17°C (59-63°F), so swimming is for the brave. This is one of the best seasons for walking the coastal promenade, cycling to Guincho, or exploring Sintra’s palaces without summer crowds. Pack layers: mornings and evenings need a light jacket even in May. See our best time to visit guide for month-by-month recommendations.
Cascais Weather in Summer (June to August)
Summer is peak season for a reason: June through August delivers reliable sunshine (11-12 hours daily) and virtually no rain. July and August both average 26°C (79°F) highs and 18°C (64°F) lows. June is slightly cooler at 24°C (75°F). The Atlantic breeze keeps humidity bearable, and sea temperatures reach their yearly maximum of 19°C (66°F) in August. Beaches like Praia da Conceicao and Praia da Rainha fill up by late morning, especially on weekends when Lisboetas drive out. Book accommodations 2-3 months ahead for July and August stays. The things to do guide covers all the summer beach and water activities.
Cascais Weather in Autumn (September to November)
September is a sweet spot: daytime highs of 25°C (77°F), sea temperatures still at 19°C (66°F), and only 25mm of rain. The summer crowds thin out after the first week of September but the weather holds beautifully through mid-October. October highs drop to 22°C (72°F) and rain picks up to 75mm. November marks the real shift: highs fall to 18°C (64°F), rain jumps to 110mm, and you will need a jacket most days. For the best autumn experience, target the second half of September through the first week of October. The events and festivals calendar lists autumn happenings including the Lumina light festival.
Cascais Weather in Winter (December to February)
Winter in Cascais is mild by European standards but wet: December and January each average 100-115mm of rain over roughly 11-12 wet days. Daytime highs reach 15-16°C (59-61°F), with overnight lows of 9-10°C (48-50°F). Frost is unknown and snow has never been recorded. You will get 5-6 hours of daily sunshine, and many winter days are bright and crisp between rain fronts. The sea drops to 14-15°C (57-59°F). Hotel rates are at their lowest, and restaurants and museums are uncrowded. A waterproof jacket and warm sweater handle most winter conditions. The neighborhoods guide covers the best areas to base yourself for a winter visit.
