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United States › California › Napa County › Climate Station ANGWIN PACIFIC UNION COLLEGE, CA US Distance 7.7 mi Normals 1991–2020

30-year climate normals

Napa County Climate and Weather Averages

Hottest month — July

84.6°

average daily high. The coldest month is December, averaging a low of 38.8°F.

Napa County gets 39.71" of precipitation a year, and 60% of it falls in Dec, Jan, Feb.

Temperature through the year

Each bar spans the average daily low to the average daily high for that month.

40° 60° 80° JanFebMarAprMayJunJulAugSepOctNovDec
MonthAvg highAvg low Precip
January 53.7° 39.3° 7.80"
February 55.9° 39.7° 7.59"
March 60.3° 40.9° 5.50"
April 65.9° 42.3° 2.37"
May 72.7° 46.7° 1.56"
June 80.0° 51.3° 0.36"
July 84.6° 54.1° 0.01"
August 84.3° 53.9° 0.04"
September 81.3° 53.4° 0.17"
October 72.4° 49.7° 1.92"
November 59.8° 42.8° 4.09"
December 52.7° 38.8° 8.30"

Rainfall by month

Napa County has a distinct wet season. 60% of the year's precipitation arrives in Dec, Jan, Feb.

January 7.80"
February 7.59"
March 5.50"
April 2.37"
May 1.56"
June 0.36"
July 0.01"
August 0.04"
September 0.17"
October 1.92"
November 4.09"
December 8.30"
Annual total 39.71"

What this climate costs you

Degree days measure how hard a building has to work to stay comfortable. They are the reason two identical houses have very different power bills, and they are the link between the weather here and what you pay every month.

Cooling degree days How much air conditioning the climate demands 604
Heating degree days How much heating the climate demands 3,375
Approximate annual cooling cost At 33.25¢/kWh, California average $201
Approximate annual electric heating cost Lower where heating is gas rather than electric $393

These are rough planning figures from degree days and the state electricity price, not a bill estimate. House size, insulation and fuel type move them a lot. See the full cost of owning a home in Napa County, where electricity is one line of eight.

Common questions

What is the weather like in Napa County?

Napa County averages a high of 84.6°F in July and a low of 38.8°F in December. Annual precipitation is 39.71 inches, with essentially no snow.

When is the rainy season in Napa County?

The wettest stretch is Dec, Jan, Feb, which accounts for 60% of the year's precipitation. That is a pronounced wet season rather than rain spread evenly through the year.

How hot does it get in Napa County?

The average daily high in July, the hottest month, is 84.6°F. That drives 604 cooling degree days a year, which is what your air conditioning has to work against.

Does it snow in Napa County?

Effectively no. Measurable snowfall is rare in Napa County.

Sources

  • Temperature, precipitation and snowfall normals — NOAA National Centers for Environmental Information, 1991–2020 Monthly Climate Normals, station ANGWIN PACIFIC UNION COLLEGE, CA US (USC00040212), 7.7 miles from the county centroid.
  • Heating and cooling degree days — NOAA, same station and period.
  • Electricity price — US Energy Information Administration, Electric Power Monthly Table 5.6.A, California residential average.
  • Wet-season share is the wettest three consecutive months as a percentage of annual precipitation, calculated from the monthly normals.