The weather year, and what each part of it does

The theory of the weather year is well covered elsewhere. This is about the version you meet in practice.

A wet winter, not a cold one

The Atlantic climate delivers most of the annual rainfall between autumn and early spring, in bursts rather than continuously. Outdoor temperatures rarely approach freezing, so it reads as mild to anyone from northern Europe. Indoors is another matter, and that is where the winter complaint actually comes from.

A waterproof and layers cover a Lisbon winter far better than a heavy coat.

Why indoors is cold

A great deal of housing was built for a warm climate with no insulation and no central heating. Single glazing, uninsulated walls and high ceilings mean interiors track the outside temperature with a lag.

Damp and condensation follow, and mould in winter is a common and genuine problem in older flats. Portable heaters and dehumidifiers are the standard local response and sell out in cold snaps.

Spring and autumn are the best of it

The shoulder seasons give long usable days, moderate temperatures and far fewer people. Rain is possible in both and rarely persistent enough to spoil a day.

Light in autumn is low and warm and is the best of the year for looking at the city. These are the months residents will tell you are the good ones.

Summer specifics

Heat builds through the day and peaks in the mid to late afternoon, which is the opposite of the common assumption. The northwesterly breeze off the estuary makes the difference between comfortable and unbearable on a given street. Stone and paving hold heat, so the centre stays warm well after dark.

Heat episodes have become more frequent and more intense in recent years, in line with the wider regional trend.

The sun is stronger than the temperature

Latitude and clear skies mean the ultraviolet index runs high through much of the year, including in spring. Reflective pale paving increases exposure at street level. Sunburn on a breezy twenty-something degree day is a standard visitor experience.

In practice, shade, hats and timing do more than any single product.

Planning around it

In summer, do the climbing and the walking early and treat mid-afternoon as indoor time. In winter, plan for shorter daylight and pick indoor options with actual heating.

In practice, check a forecast for wind and for the specific location, because the hills west of the city have their own weather. No month here is unusable, which is more than most European capitals can say.

None of this is a substitute for talking to a clinician if something feels wrong.

Summer air and distant fires

Wildfires in the interior during the hot months can push smoke a long way, and the city occasionally gets a hazed sky and the smell of burning from fires nowhere near it. The signs are an orange cast to the light and a flat white sky on a day the forecast promised would be clear, which is a smoke layer rather than ordinary cloud.

Where it helps most, air quality on those days is genuinely worse, and anyone with asthma or another respiratory condition should follow the guidance of a qualified professional rather than judging it by how the sky looks. This is an intermittent matter of a few days rather than a season, but it is worth knowing about before committing one of them to a long walk along an exposed ridge.

The takeaway

Pack layers and a waterproof, not a heavy coat, and expect the cold to be indoors.

Small and repeatable beats ambitious and abandoned, almost every time.