Napa (CA) Temperature by Month

The average annual maximum temperature in Napa, California, United States of America is 23°C (73°F), with daytime highs ranging from 14°C (57°F) in December to 30°C (86°F) in September. This page covers monthly averages, day-night differences, and how Napa compares to cities worldwide.

Depending on the time of the year, temperatures range from comfortable to mild in Napa. At night, minimum temperatures range from 12°C (54°F) in September to 4°C (39°F) in December.

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

From around 4 AM to 6 AM temperatures are at their lowest; by 3 PM they've climbed to their daily peak. September, the warmest month, averages 275 hours of sunshine.

The chart below shows the average temperature throughout the year:

Napa's average annual maximum temperature is 23°C (73°F). To put that in context, here's how it compares to a few well-known destinations:

Seville, Spain averages 23°C (73°F) a year, one of the warmer cities in Western Europe, with long hot summers.

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

Chicago, USA averages 15°C (59°F) annually, known for extreme seasonal swings, from bitterly cold winters to warm summers.

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

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 Napa's weather, including monthly rainfall, sunshine hours, and humidity, visit our Napa climate page.