Cascais in December: Weather, Crowds, Prices and a Two-Day Coast Plan

CASCAIS · DECEMBER · 38.7° N

December hands Cascais a thermometer that barely moves and a clock that does. Days average 58.8°F, nights 47.7°F, and on December 15 the sun is up for 9 hours 31 minutes, rising at 7:46 a.m. and setting at 5:17 p.m. local time. Portugal stays on UTC through the winter, so those are the hours you get, and they fall early.

The trade is written in the rain column: 3.94 inches spread over 9.7 days with measurable rain. That leaves roughly two days in three dry, which is a walking month on this coast and a poor bet for a swimming trip. If the water is the reason you booked, the 12-month view of Portugal will move your dates before we do.

On this page

• Average highs, lows and rain daysCascais weather in December, from IPMA
• What to wear at 9 a.m. and at 3 p.m.Day highs, night lows and the frost question
• Hotel prices and when to bookWhat we can and cannot price for December
• Things to do on a dry December dayCabo Raso, the Guincho dunes and Pedra Amarela
• A two-day plan around 9h 31m of lightThe December itinerary, hour by hour
• December or November or January?How the three months compare on rain and temperature
• Is December worth the flight?Our verdict, and who should shift dates

Every figure here is a 1991-2020 normal from IPMA unless the line says otherwise. Where we could not verify something (a sea-surface reading, a museum hour, a lodging-tax rate) we say so rather than fill the gap with a plausible number. For the parts of Cascais that do not change with the calendar, and for the day trip up to Sintra, those pages carry the detail.

Cascais weather in December: average highs, lows and rain days

These normals come from IPMA, Portugal’s national weather service, and specifically from its 1991-2020 series for station 579, Lisboa/Gago Coutinho: average high 58.8°F, average low 47.7°F, 3.94 inches of precipitation. That is a real thermometer rather than a model grid cell, and it sits inland at the airport, 341 feet (103.9 m) above sea level. Cascais faces the open Atlantic, so it runs cooler and windier than the reading, and the serra behind the coast is colder and far wetter again. Pack for the shore with the normals above, not for a ridge trail.

Nine point seven days in an average December record at least 1 mm of rain, which is 0.04 inch, and 3.5 days record 10 mm (0.39 inch) or more. Those are IPMA’s thresholds, not the 0.10-inch threshold American tables use, so the counts are not interchangeable with a NOAA column. In practice: something measurable about one day in three, a genuine soaking roughly one day in nine, and about twenty-one days of the month with nothing on the gauge at all.

Between the average high and the average low sits 11.1°F, which is a narrow swing by winter standards and a useful one for packing. One warm mid-layer covers the whole day, and the variable is wind, not cold. On an exposed shore a hooded shell beats an umbrella by a wide margin, and the umbrella you buy at 10 a.m. usually dies by noon. Our packing page has the rest of the list.

Light is the real constraint of the month. On December 15 the sun rises at 7:46 a.m. and sets at 5:17 p.m., for 9 hours 31 minutes, and usable brightness on the coast is gone by roughly 5:45. Build outdoor plans between 10 and 4, put lunch somewhere you can linger, and accept that dinner happens after dark whatever time you sit down.

How warm is Cascais in December? Day highs, night lows and frost

The month averages 58.8°F by day and 47.7°F at night, an 11.1°F spread that holds steady from the first week to the last. Nothing in the IPMA series suggests a warm half and a cold half of December on this coast. What you feel instead is the wind, which the airport station under-reads by its own geography.

At 9 a.m. that means a long-sleeve base, a fleece and a windproof shell, with the shell on from the moment you reach the seafront. By two or three in the afternoon, on a dry day in the sun, the fleece usually comes off and stays off for two hours. After sunset at 5:17 p.m. you want all three layers back, plus something for the ears if you are walking the promenade rather than sitting down to eat.

On frost, we have the monthly mean low and nothing on the distribution of nights behind it. We could not verify a count of December nights at or below 32°F at station 579, so we publish no frost figure and no minimum extreme. A mean low of 47.7°F leaves little room for one at sea level, and we offer that as judgment, not as a measurement. The serra is a separate question, and this station does not answer it.

How busy is Cascais in December? Crowds, prices and the demand peak

December falls outside the European summer holidays, which is a calendar fact rather than a price reading. Beyond that we can say very little with numbers: we found no occupancy series and no monthly room-rate series for Cascais, so we crown no month cheap and no month expensive here. What a Portugal trip costs across the year, in tiers rather than quotes, sits on our trip-cost page.

One dated pressure is undeniable: Christmas and New Year fall inside this month, and those nights move first while the middle weeks of December stay open longer. Lead-time data for Cascais we could not verify, so treat the order as editorial judgment. Fix the holiday nights before anything else, keep the midweek nights flexible, and buy the transatlantic seat before the room, since that is the line that swings hardest. Flights from the US covers the routings.

On the municipal lodging tax, we could not verify a rate for Cascais, or whether one applies to your nights at all, so no percentage appears here. Ask at check-in and expect it as a separate line on the folio rather than inside the room rate. The general run of Portuguese paperwork and small charges is on the know-before-you-go page.

Spend the extra money on a car, not on a sea-view upgrade you will look at in the dark. The Sintra-Cascais Natural Park spreads across 14,583 hectares (about 36,000 acres), Cabo Raso and the Guincho dunes sit well outside town, and with sunset at 5:17 p.m. the car is what turns a five-hour daylight window into three stops instead of one. Our rental guide and the transport page have the mechanics.

Things to do in Cascais in December

Walking is what this month unlocks. Ground that punishes you in high summer is comfortable at 58.8°F, the light stays low and sideways all day, and the two raptors that nest in the park, the peregrine falcon and Bonelli’s eagle, are hunting over open country you can actually cross on foot. The park also protects most of the region’s endemic and threatened plants, concentrated in the serra rather than along the shore.

Three named targets carry the month. Cabo Raso, with the coastal lapies running north of it, a karst relief the ICNF calls one of the rare geological forms of this coast. The Guincho-Oitavos dune system, with the habitats that survive on moving sand. And Pedra Amarela, rising to 1,332 feet (406 m) in the serra behind the coast.

None of that rock moves with the season. The limestone north of Cabo Raso is the same in August as on December 20, and the dunes shift with the wind rather than the calendar. What December changes is the air above them: 4.9°F cooler than November’s 63.7°F average high, with 0.57 inch less rain in the month. That gap is the whole argument for walking the coast now instead of in the warm half of the year.

We could not verify an entry fee, a free-admission day or a December opening hour for any Cascais site, so we quote no prices. What the ICNF brochure does establish is the legal frame: the area was protected as a Protected Landscape by Decree-Law 292/81 of October 15, 1981, then reclassified as a Natural Park by Regulatory Decree 8/94 of March 11, 1994, with its management plan approved the same day.

Cascais in December: a two-day itinerary

Day one belongs to the coast. Breakfast before sunrise at 7:46 a.m., on the seafront by 9:30 while the air is still near the overnight 47.7°F, then drive out to Cabo Raso around 11 and walk north along the lapies for an hour. Lunch inland and unhurried at one, because you want the 2:30 to 4:30 block for the Guincho-Oitavos dunes with the sun low behind them. Sunset at 5:17 p.m. ends the outdoor day, and dinner follows in the dark.

Day two goes up. Start into the serra by nine for Pedra Amarela at 1,332 feet, allow for weather that is colder and far wetter than the coastal normals, and come down through Colares, whose wine keeps its international name and whose orchards grow the Colares reinette apple, the rose peach, the thick-skinned lemon and the pearl pear. On one of the month’s 3.5 heavy-rain days, drop the ridge and give the day to town and to Sintra, calling ahead, since December hours we could not verify.

Cascais in December vs November and January

Across the three months the temperature drop is front-loaded: November to December costs 4.9°F on the daytime average and 4.5°F at night, while December to January costs only 0.9°F and 1.7°F. Rain runs the other way, falling from 4.51 inches in November to 3.94 in December and 3.78 in January, even as the count of wet days creeps up from 9.3 to 9.9. On the water, no column appears, because we could not verify a sea-surface series for Cascais. Sea tables published elsewhere usually average daily maxima, which reads warmer than a 24-hour mean, and we will not borrow a number we have not checked.

Shift four weeks earlier and you buy warmth at the price of water: November’s 63.7°F days and 52.2°F nights, against 0.57 inch more rain in the month. Shift four weeks later and you save another 0.16 inch of rain, spread across 0.2 more wet days, for nights that sit 1.7°F colder. Our January page runs those numbers out in full, including what the short days do to a two-day plan.

Is December a good time to visit Cascais?

Yes if you came to walk, to eat well and to pair the coast with a city base, and no if the trip was built around the water. Twenty-one dry days out of thirty-one, 58.8°F afternoons and a park of 36,000 acres at your back make a strong four-night case, especially bolted onto Lisbon. Beach loungers and swimmers are booking the wrong month, and nothing in the normals argues otherwise.

For readers whose answer came out no, November is the nearer correction: 4.9°F warmer by day, 4.5°F warmer at night, at a cost of 0.57 inch more rain across 0.4 fewer wet days. Anyone who wants real swimming weather should leave the winter alone entirely and work from the 12-month verdict, which puts the warm months in order.

What December alone gives you: 9 hours 31 minutes of light on the 15th, with sunset at 5:17 p.m., so the best hour on the Guincho dunes falls before dinner rather than long after it.

The last word

Book the car, then decide each morning which half of the park gets the day, because the weather decides it for you nine or ten times in thirty-one. And save one climb for the least accessible corners of the serra: that is where the remnant oak forest survives, holly among it, a threatened species you are not going to see from the promenade. Four nights covers both halves with a spare day for the rain.

Sources & data for this guide

• December normals (58.8°F / 47.7°F, 3.94 in) and rain-day counts at 1 mm and 10 mm · IPMA, 1991-2020 climate normals, station 579 Lisboa/Gago Coutinho, altitude 103.9 m · checked Sep 23, 2026
• November and January normals used in the comparison table · same IPMA series and station · checked Sep 23, 2026
• Daylight, sunrise 07:46 and sunset 17:17 UTC on December 15, converted to local time · sunrise-sunset.org · checked Sep 23, 2026
• Park area, legal history, Cabo Raso lapies, Guincho-Oitavos dunes, Pedra Amarela, raptors, Colares fruit varieties · ICNF, brochure « Conheça o Parque Natural de Sintra-Cascais », icnf.pt · checked Sep 23, 2026
• What we could not verify: no sea-surface temperature series, no trail length, no parking count, no site opening hour, no entry fee and no lodging-tax rate for Cascais · reading note · Sep 23, 2026
• The station stands inland at the airport, 341 feet up; Cascais runs cooler and windier and the serra wetter · hours and tariffs change, check operators when you book.

To plan your stay

• Best Time to Visit Cascais: Month-by-Month Weather, the Quiet Months and the One to Skip
• Cascais in January: Weather, Rain Days, Crowds and What to Pack
• Cascais in November: Weather, Rain Days, Daylight and What to Pack
• Cascais in February: Weather, Rain Days and a Two-Day Plan

Nearby places

• Ericeira, Portugal: the Surf Reserve, the Beaches by Level and Where to Stay
• Sintra, Portugal: Pena, Regaleira, Tickets and the One-Day Plan
• Pena Palace Tickets and Visit Guide: Prices, Time Slots and Crowd Strategy