CASCAIS · AUGUST · 38.7° N
August hands Cascais its warmest days of the summer and almost none of its rain. The 1991-2020 normals put the average high at 84.2°F, the average low at 65.3°F, and the whole month’s precipitation at 0.20 inches. An average August records measurable rain on a single day. On August 15 the sun is up for 13 hours 43 minutes, which leaves the coast, the headland and a long dinner outdoors inside one day.
What the date takes back is room to move. This is high summer on the Estoril coast, when European school holidays overlap and Lisbon’s day-trippers arrive by the trainload. Our Cascais guide handles where to sleep and how to get in from the airport. The question for a date, not a place, is whether the driest stretch of the year is worth the company.
THE MONTH AT A GLANCE · CASCAIS · AUGUST
August is the warmest and driest of the three summer months in the Cascais normals, and the most crowded: take it if your trip is built on water and long evenings, shift to September if it is built on quiet.
AVG HIGH 84.2°F · 0.20 IN OF RAIN · ONE WET DAY · 13H43M OF LIGHT ON AUG 15
Go for: a month where one rain day out of 31 lets an outdoor plan stand, with light until 8:32 p.m. and the coast of a 36,035-acre natural park at the end of the road.
Think twice before: booking late, or expecting the serra trails to yourself: August is the fullest month of the coast’s year.
Normals: IPMA station 579 · Daylight: sunrise-sunset.org · Park: ICNF · full sources at the end
On this page
- Cascais weather in AugustThe 1991-2020 normals, and where the thermometer sits
- How warm does it get, day and night?84.2°F afternoons, 65.3°F nights, and the water question
- How busy Cascais gets in AugustHigh summer, booking lead time, what we could not price
- Things to do in Cascais in AugustSintra-Cascais Natural Park, Cabo Raso, the Guincho dunes
- A two-day plan for a summer weekendTwo days built on 13 hours 43 minutes of light
- August vs July and SeptemberHow the three months compare on heat and rain
- Is August a good time to visit Cascais?Who should go, and who should move four weeks
July and September are measured at the same station over the same 1991-2020 period, so the comparison below is like for like, with no estimates in either column. Trains and car hire from Lisbon sit in getting around Portugal.
Cascais weather in August: average highs, lows and rain days
| August in Cascais | 1991-2020 normal |
|---|---|
| Average high | 84.2°F (29.0°C) |
| Average low | 65.3°F (18.5°C) |
| Precipitation, whole month | 0.20 in |
| Days with 1 mm (0.04 in) or more | 1.0 |
| Days with 10 mm (0.39 in) or more | 0.1 |
| Daylight, August 15 | 13 h 43 min |
| Sunrise / sunset, August 15 | 6:49 a.m. / 8:32 p.m. local |
Every figure here comes from one place: IPMA, the Portuguese national weather service, and its 1991-2020 normals for station 579, Lisboa Gago Coutinho. That is a real thermometer at 341 feet (103.9 m), not a model grid cell. It also sits inland, at Lisbon’s airport, while Cascais faces the open Atlantic and runs cooler and windier than the station that supplies its numbers. Read 84.2°F as the warm end of a coastal day, and expect the serra behind the town, higher and far wetter, to behave differently again.
Rain barely registers. One day in an average August records at least 1 mm, which is 0.04 inch, and 0.1 day records 10 mm or more, so a real soaking turns up about one August in ten. Those thresholds are IPMA’s own, not the 0.10-inch cutoff American tables use, and the two counts do not swap. Translated into a week of plans: one outdoor day out of 31 may want a roof, and losing a whole afternoon is a long shot.
Day and night are 18.9°F apart, and the Atlantic wind widens that gap on the exposed side of the headland. A swimsuit and a linen shirt carry the afternoon. For 9 p.m. on a terrace at 65.3°F with a breeze off the water, pack a light sweater or a windbreaker, plus something that will not flap on the dune path at Guincho. Our Portugal packing guide has the rest.
Light runs 13 hours 43 minutes on August 15, sunrise at 6:49 a.m. and sunset at 8:32 p.m. local time. Dinner starts in daylight for most of the month. That length also buys a genuine two-shift day: the coast in the morning before the heat peaks, two shaded hours after lunch, then back out at six with two and a half hours of light in hand.
How warm is Cascais in August? Daytime highs, night lows and the sea
August tops its two neighbors at both ends of the thermometer: 84.2°F by day against July’s 82.9°F and September’s 80.2°F, and 65.3°F at night against 64.4°F and 63.3°F. Four degrees separate the warmest of the three from the coolest by day, and two degrees separate their nights. Nobody arrives in Cascais in summer and finds a different climate from one month to the next, which is exactly why the rain column matters more than the heat column.
Mornings before ten deserve a second thought. At a coastal low of 65.3°F with the ocean beside you, a t-shirt alone is thin on a breakfast terrace. By 2 p.m. the same day is climbing toward 84.2°F and every scrap of shade is spoken for. Water shoes, a hat and a refillable bottle cover the afternoon; the evening wants the layer you packed for it.
Freezing nights are not a question in August, and the margin is not close: the month’s average low sits 33.3°F above freezing. As for the water, we could not verify a sea-temperature series for Cascais, so we give no figure. One caution for whatever table you find elsewhere: sea temperatures are normally published as an average of daily maxima, which reads a little warmer than a true 24-hour mean.
How busy is Cascais in August? Crowds, prices and the demand peak
August is the fullest month of the coast’s calendar, the stretch when European school holidays stack on top of one another and the Lisbon line runs busy all day. That much is a fact of the calendar. Ranking the month by price is another matter: we found no occupancy series and no monthly room-rate series for Cascais, so we crown no month expensive and quote no nightly figure.
Book early all the same. For an August weekend we would lock a room by spring, and eight to twelve weeks out at the very latest (est.), which is also when transatlantic fares stop cooperating. Three nights is a sane minimum for a coast base with a Sintra day attached. Compare bases in where to stay in Portugal, shape the budget with what a Portugal trip costs, then price the flight in flights from the US.
On the tourist tax we have nothing verified. We could not confirm whether Cascais charges a per-night levy, or at what rate, so no amount comes from us. Ask when you reserve: where a levy of that kind applies in Portugal, it is normally settled at the property rather than folded into the online price.
If one line of the August budget deserves stretching, make it the car. The Sintra-Cascais Natural Park spreads across two municipalities, and its best hours are at the ends of the coast road, well past where a town stay leaves you. Two days of rental beat four days of waiting for a ride, and our car rental guide covers the tolls and the insurance line that catch Americans out.
Things to do in Cascais in August: Sintra-Cascais Natural Park, Cabo Raso and Guincho
An average August records rain on one day out of 31, and that is why an outdoor itinerary holds this month in a way September’s does not: the next month brings 1.41 inches across 3.7 days at 1 mm or more. Add 13 hours 43 minutes of light and the coast, the serra and a late dinner fit into a single day without a backup plan for either end of it.
Sintra-Cascais Natural Park covers 14,583 hectares, about 36,035 acres, across the municipalities of Sintra and Cascais. It was first 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. Inside it sit the coastal lapies north of Cabo Raso, a rare karst relief, the Guincho-Oitavos dune system, and Pedra Amarela at 1,332 feet (406 m) in the serra behind the shore.
The lapies and the dunes read the same in February as in August. What August changes is the air above them: 84.2°F instead of September’s 80.2°F, and one rain day instead of nearly four. The park also holds nesting peregrine falcons and Bonelli’s eagles, plus remnant oak forest in its least accessible corners, where threatened holly, Ilex aquifolium, still survives.
The ground itself costs nothing, as far as we can tell: we could not read a single opening hour, trail length or beach measurement for Cascais. The ICNF brochure describes the protected area without those figures, and the municipal site publishes an events agenda rather than data we could use. We also verified no August event date, so we name no festival.
Cascais in August: a two-day itinerary
Day one runs on the light. Out by 7:30, while the air is still near the 65.3°F end, coffee on the way, and the first two hours on the coast before the heat climbs. Late morning in the water or on the sand. Lunch indoors from 1 p.m., with the two hottest hours of an 84.2°F day spent under a roof. Back out at 5:30 toward Cabo Raso and the karst coast, sunset at 8:32 p.m., dinner after it.
Day two goes up and inland: the serra side of the park with Pedra Amarela’s 1,332 feet on the skyline, a slow stop at the Guincho-Oitavos dunes coming back, then the harbor for the evening. If the month’s one wet day lands on yours, the train into Lisbon converts it into a museum afternoon, and at 0.1 day per August with 10 mm or more, a washout across both days is unlikely.
Cascais in August vs July and September
| Measure | July | August | September |
|---|---|---|---|
| Average high | 82.9°F | 84.2°F | 80.2°F |
| Average low | 64.4°F | 65.3°F | 63.3°F |
| Precipitation, whole month | 0.11 in | 0.20 in | 1.41 in |
| Days with 1 mm (0.04 in) or more | 0.4 | 1.0 | 3.7 |
| Sea temperature | Not verified | Not verified | Not verified |
Side by side, the three months sit close on temperature and far apart on rain. July runs 82.9°F by day, 64.4°F at night and 0.11 inches across 0.4 days at 1 mm or more. August adds 1.3°F to the afternoon and 0.20 inches over one day. September drops to 80.2°F and 63.3°F, then multiplies the rain by seven, 1.41 inches across 3.7 days, all from the same station and the same 1991-2020 period.
Move four weeks later and you gain an emptier coast while losing four degrees of afternoon and most of the dry run. Move four weeks earlier and July gives you marginally less rain than August, 1.3°F less warmth, and the same crowded summer. Read the neighbors in full in Cascais in July and Cascais in September, or the twelve-month view in the best time to visit Portugal.
Is August a good time to visit Cascais?
Yes, if the trip is built on water, long evenings and a plan you would rather not rewrite. Days at 84.2°F, a single rain day and 13 hours 43 minutes of light are what the normals promise. No, if a full town wears you out fast, or if the point of the trip is the serra trails with nobody on them.
When the answer is no, September is the shift, and its price is written down: 80.2°F instead of 84.2, and 1.41 inches of rain over 3.7 days instead of 0.20 over one. For an ocean-first vacation that trade goes the wrong way. For walking up toward 1,332 feet and eating dinner without a wait, September wins by a distance.
No other month of the three puts 84.2°F afternoons, a month-long rain total of 0.20 inches and nearly fourteen hours of daylight in the same square of the calendar.
The last word
Book the room before the summer fares move, give Cascais three nights, and set one of them aside for the park rather than the promenade: 36,035 acres of it start a short drive from the harbor. One more thing the ICNF brochure records, and nobody puts on a postcard: this is Colares country, a wine that kept its international name, in an area that grows fruit varieties of its own, the Colares reinette apple, the rose peach, the thick-skinned lemon and the pearl pear. Order the ones you have never heard of.
Sources & data for this guide
- August normals, highs, lows, precipitation and rain-day counts · IPMA, climatological normals 1991-2020, station 579 Lisboa Gago Coutinho, 341 feet (103.9 m) · checked Sep 23, 2026
- July and September normals, same station and same 1991-2020 period, not estimates · IPMA · checked Sep 23, 2026
- Daylight, sunrise and sunset for August 15, converted from UTC to local time · sunrise-sunset.org · checked Sep 23, 2026
- Park area of 14,583 hectares, Decree-Law 292/81 and Regulatory Decrees 8/94 and 9/94, coastal lapies at Cabo Raso, Guincho-Oitavos dunes, Pedra Amarela at 406 m, nesting peregrine falcon and Bonelli’s eagle, remnant oak forest and holly, Colares wine and fruit varieties · ICNF brochure « Conheca o Parque Natural de Sintra-Cascais », icnf.pt · read Sep 23, 2026
- Editorial admission: we found no sea-temperature series, no verified tourist-tax rate, no occupancy or room-rate series, no opening hour, no trail length, no beach measurement and no August event date for Cascais · checked Sep 23, 2026
- Acre and foot conversions are ours, from the metric figures above · 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 July: Weather, Rain Days, Crowds and How It Compares to June and August
- Cascais in September: Weather Normals, Rain Days and How It Compares to August and October
- Cascais in June: Weather, Rain Days, Crowds and a Two-Day Plan