Viana do Castelo Temperature by Month

Viana do Castelo, Norte Region, Portugal has an average annual maximum temperature of 19°C (66°F), with moderate seasonal shifts ranging from 14°C (57°F) in January to 24°C (75°F) in August. Below you'll find a full monthly breakdown and a comparison with cities worldwide.

Viana do Castelo sees moderate fluctuations in temperatures, making each season distinct yet not extreme. Nights are considerably cooler, with lows ranging from 16°C (61°F) in August to 8°C (46°F) in January.

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

Daily lows are most common between 4 AM and 6 AM. By 3 PM temperatures reach their daily high, driven by peak solar heating. August, the warmest month of the year, receives 295 hours of sunshine.

The chart below shows the average temperature throughout the year:

Viana do Castelo's average annual maximum temperature is 19°C (66°F). To put that in context, here's how it compares to a few well-known destinations:

Rome, Italy averages 20°C (68°F) annually, with reliably warm summers and comfortable winters.

Queenstown, New Zealand averages 10°C (50°F) annually, remember seasons are flipped, so its coldest months fall in June and July.

Seoul, South Korea averages 18°C (64°F) a year, with four clear seasons, cold winters, and hot humid summers.

Brisbane, Australia averages 26°C (79°F) a year, with warm winters and hot, humid summers.

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 Viana do Castelo, January is the coolest month, with average highs of 14°C (57°F) and humidity around 81%, 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.

For cities and regions with significant elevation, altitude is one of the biggest factors shaping local temperatures. As a rule of thumb, temperatures fall by around 6°C for every 1,000 metres gained, so a city at 2,000 metres will typically be around 12°C cooler than a city at sea level in the same region. Higher ground also tends to see more dramatic day-to-night temperature swings, since thinner air loses heat faster after sunset.

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