Altarnun Temperature by Month

The average annual maximum temperature in Altarnun, Cornwall, United Kingdom is 15°C (59°F), with daytime highs ranging from 10°C (50°F) in January to 20°C (68°F) in July. This page covers monthly averages, day-night differences, and how Altarnun compares to cities worldwide.

Seasonal changes in Altarnun bring a little variety without extreme temperature swings. Nighttime lows range from 13°C (55°F) in July to 4°C (39°F) in January.

The chart below illustrates the average maximum day and minimum night temperatures in Altarnun 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. July, the warmest month of the year, receives 215 hours of sunshine.

The chart below shows the average temperature throughout the year:

Altarnun's average annual maximum temperature is 15°C (59°F). To put that in context, here's how it compares to a few well-known destinations:

Athens, Greece sits at 23°C (73°F) on average, with hot dry summers and mild winters characteristic of the Mediterranean.

Toronto, Canada averages 13°C (55°F) annually, with cold snowy winters balanced by genuinely warm summers.

San Francisco, USA averages 19°C (66°F) annually, but with little seasonal variation, summers are often cool and foggy, winters mild.

Perth, Australia averages 25°C (77°F) annually, with a classic Mediterranean climate, hot dry summers and mild wet winters.

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 the cooler months, when temperatures drop below 10°C, high humidity makes the cold feel more cutting than it would in dry conditions.

In Altarnun, January is the coolest month, with average highs of 10°C (50°F) and humidity around 86%, considered very 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 Altarnun's weather, including monthly rainfall, sunshine hours, and humidity, visit our Altarnun climate page.