Oeiras Temperature by Month

The average annual maximum temperature in Oeiras, Lisbon Region, Portugal is 20°C (68°F), with daytime highs ranging from 15°C (59°F) in January to 24°C (75°F) in August. This page covers monthly averages, day-night differences, and how Oeiras compares to cities worldwide.

The moderate changes in the climate in Oeiras ensure gradual weather shifts through each season. At night, temperatures drop to between 18°C (64°F) and 11°C (52°F) depending on the time of year.

The chart below illustrates the average maximum day and minimum night temperatures in Oeiras by month:

Temperatures tend to bottom out between 4 AM and 6 AM, then climb to their daily peak around 3 PM. August, the warmest month, sees 355 hours of sunshine.

The chart below shows the average temperature throughout the year:

Oeiras's average annual maximum temperature is 20°C (68°F). To put that in context, here's how it compares to a few well-known destinations:

Lisbon, Portugal averages 21°C (70°F) annually, warm summers, mild winters, and rain mainly in the cooler months.

On the cooler end, Oslo, Norway averages just 10°C (50°F) annually, with pleasant summers but long, cold winters.

Beijing, China averages 20°C (68°F) annually, but with big seasonal swings, very cold winters and hot summers.

Adelaide, Australia averages 21°C (70°F) a year, with warm summers, mild winters, and relatively low rainfall year-round.

Temperature alone doesn't tell the whole story, humidity plays a big role in how warm or cold it actually feels. High humidity in summer makes the heat feel more intense, particularly once temperatures climb above 25°C. In winter, the same humidity can make cold air feel sharper than the thermometer suggests.

In Oeiras, January is the coolest month, with average highs of 15°C (59°F) and humidity around 82%, considered very high. In August, the warmest month, temperatures average 24°C (75°F) with 73% humidity, conditions that feel high. For a full picture, see our humidity page.

Climate temperature data is typically calculated as a 30-year average. This smooths out year-to-year variability and gives a more reliable picture of what a place is actually like, rather than what happened in any single unusual year.

The readings come from a range of sources, land-based weather stations, ocean buoys, ships, and satellites. That data is collected by weather services around the world, then pooled, quality-checked, and averaged to produce the climate records you see here.

Whether a city sits on the coast or deep inland makes a significant difference to its climate. Coastal areas tend to have more stable temperatures year-round, large bodies of water absorb heat slowly in summer and release it gradually in winter, keeping extremes in check. Cities far from the sea don't benefit from that buffer, which is why continental climates tend to have hotter summers and colder winters than their coastal counterparts at the same latitude.

For more on Oeiras's weather, including monthly rainfall, sunshine hours, and humidity, visit our Oeiras climate page.