Climate of Lisbon

Lisbon and its metropolitan area feature a mild subtropical or a Hot-summer Mediterranean climate (Köppen: "Csa"), with short and mild winters and warm to hot summers. According to Troll-Paffen climate classification, Lisbon has a "warm-temperate subtropical" climate ("Warmgemäßigt-subtropisches Zonenklima"). According to Siegmund/Frankenberg climate classification, Lisbon has a subtropical climate.
Temperature.
Normals.
Lisbon has mild to warm, moderated temperatures, winters are very mild for its latitude, influence of the Portugal Current, a weak current by-product of the Gulf Stream, average highs during this season vary between . Lisbon has the mildest winter nights out of any major European city, ranging between . Summers are warm to hot, though due to the upwelling phenomena in the western coasts of its metropolitan area, maxima in summer has dramatic fluctuations depending on the location. Regions east of the Tagus Estuary usually average around maxima in July and August, while western areas close to the coast, such as Cascais or Sintra, will usually average around maxima, reaching as far as in Cabo da Roca. Costa da Caparica does not have such strong upwelling conditions and is usually hotter in the summer than the aforementioned coasts. Summer nights are often independent on the location, averaging a comfortable .
Extremes.
Lisbon's location on the westernmost side of continental Europe makes it much less vulnerable to both heatwaves and coldwaves, though outbrakes of the Saharan Air Layer can sometimes push the temperatures above as it happened as part of the 2018 European heat wave, skies were a shade of white due to the extreme concentrations of airborne dust particles. Temperatures in two of Lisbon's stations reached an all-time high of on 4 August of that same year. The third station (Tapada da Ajuda) recorded .
The coldest temperatures ever recorded in the city were on 15 January 1985 and on 11 February 1956.
In a normal year, the recorded maxima can go anywere from in the winter and in the summer, and the minima from in the winter and in the summer. Temperatures behond these are usually considered irregular and limited to exceptional years. Lisbon is on the USDA hardiness zone 10b.
Precipitation.
Lisbon can be described both as a moist and a dry city depending on the season of the year. Precipitation is most common in Autumn and Winter which is therefore the greenest time of the year. Summers in Lisbon tend to be very dry due to the Azores high though exceptions happen and low-pressure areas can come into play bringing more than average rains but still avoiding a wet summer (>). Foggy mornings are also common in the summer, especially in coastal areas and can bring drizzle which can sometimes be observed early in the day in wet roads and calçada near shady areas.
Lisbon has on average 112 precipitation days a year of which around 30% is drizzle (below ). The driest months, July and August, have on average two days of precipitation ( of which 50% is drizzle), and the wettest months, November and December, have on average 12–15 days of precipitation and around . December is the rainiest month of which half the days receive some form of precipitation. The average annual precipitation is .
Humidity.
In the same way precipitation varies greatly from month to month, the average relative humidity also experiences considerable seasonal changes. Lisbon has very humid winters, averaging 78-80% humidity. This humidity also ads to its mildness but can also result in muggy conditions in the most humid winter days, especially in closed spaces with no air filtration. The air in the summer is otherwise dry, 60 to 65%, and is particularly variable, often going below 40% during the day and 70% at night.
Sunshine.
Lisbon is a sunny city, in fact, it is the sunniest capital city in mainland Europe and one of the sunniest overall places in southern Europe, with more than 2,800 yearly sunshine hours despite the relatively high yearly precipitation. Sunshine and precipitation stack up oppositely with the dullest month being also the rainiest (December) which has around 140-150 total hours. Despite July having the most sun hours, August is on average the sunniest month with around 80% chance of direct sunlight hitting the ground.
In the Lisbon area, sunshine hours reach their maximum value in the southwestern Setúbal Peninsula (near Cabo Espichel), and their lowest in the Sintra Mountains and parts of the northwest District.
Daylight.
Due to its southern position in Europe, Lisbon has a rather optimal number of hours of daylight. Winter days are not as short as in the northern part of the continent and summers have at least 9 hours of nighttime. The average duration of daylight in the wintertime is 10.3 hours (for comparison: London or Moscow or Warsaw have about 8 hours).
Wind.
Lisbon is generally still, though it can become quite windy in occasional Atlantic storms, acompanied by rain. The average wind speed depends largely on the area. Tapada da Ajuda has almost no sign of wind, other areas such as Gago Coutinho, near the airport, get double that wind speed. The District of Lisbon, especially the west, is one of Portugal's windiest zones. Cabo da Roca has registered wind gusts of up to .
Sea temperature.
As with the rest of Portugal, ocean temperatures are extremely moderate and cool year-round, only varying between the coldest and warmest month. The coolest months are February and March (around ) while the warmest are from August through October (around ). The average annual sea surface temperature is around .