Climate averages 1991–2020

Napa weather
in July.

A hot, very dry month: the warmest and the driest of the year.

Long-term climate patterns, not a forecast for a particular trip.

Average high 30.7°C Daytime mean, July

Average low 14.7°C Night-time mean, July

Rainfall <1 mm Almost no rain

Daylight 15 h Sunrise to sunset, per day

July is a hot month in Napa: daytime highs average 30.7°C and nights cool to about 14.7°C. By daytime temperature it is the warmest month of the year.

Rain is very rare: less than 1 mm falls in a typical July (the driest month of the year). Daylight, from sunrise to sunset, lasts about 14 h 33 min on an average July day.

The nearest other city in this atlas is Vallejo (22 km away). In July its highs average 28.5°C, 2.2°C cooler than Napa, with almost no rain (under 1 mm).

Among the 498 cities listed in the United States, Napa ranks joint 218th of 498 for the warmest July highs and joint 9th of 498 for the driest July (rainfall, lowest first). The mean July high of those 498 cities is 30.3°C; Napa is 0.4°C warmer than that mean.

From July to August, average highs fall by 0.1°C to 30.6°C, and monthly rainfall stays under 1 mm.

The annual picture

July in context

30-year average

Average highAverage low°C

Monthly rainfall

Average total · mm

Averages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated

Every month, side by side

Napa climate table

1991–2020

Monthly climate averages for Napa, 1991–2020
Month	Average highHigh / low	Average low	Rainfall mm/month	Rain days ≥1 mm/day	Daylight hours/dayDaylight h/day
January	14.4°C5.3°C	5.3°C	116	9.4	9.810 h
February	15.9°C6.3°C	6.3°C	117	8.7	10.711 h
March	18.0°C7.5°C	7.5°C	86	8.4	11.912 h
April	20.7°C9.0°C	9.0°C	38	4.9	13.213 h
May	24.6°C11.5°C	11.5°C	20	3.2	14.214 h
June	28.9°C13.9°C	13.9°C	4.7	0.9	14.815 h
July, selected	30.7°C14.7°C	14.7°C	0.4	0.1	14.515 h
August	30.6°C14.9°C	14.9°C	0.7	0.2	13.714 h
September	29.5°C14.6°C	14.6°C	2.0	0.4	12.512 h
October	25.1°C12.6°C	12.6°C	26	2.9	11.211 h
November	18.3°C8.4°C	8.4°C	56	5.9	10.110 h
December	14.2°C5.6°C	5.6°C	110	9.4	9.610 h

Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.

Compare places

July in nearby cities

Distance from Napa

Read the numbers correctly

Climate, not a promise.

These patterns help compare months. They cannot tell you the weather on a specific day of your trip.

Sources, method and limits

How these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Napa) is explained once on the Napa year overview and on the Sources, method and limits page.