Napa, CA weather in August
August in Napa: warm and dry. Highs 84°F, lows 56°F, rain is rare. This is the peak of the warm season in Napa. A good month for most outdoor plans.
- Normal high
- 84°F
- Normal low
- 56°F
- Wet days
- 0
- 0.06 in total
- Muggy days
- 0
- dew point 65°F+
How August changes from start to finish
| August 1 | August 31 | |
|---|---|---|
| Normal high | 83°F | 85°F |
| Normal low | 56°F | 55°F |
| Chance of a wet day | 0% | 1% |
| Sunrise / sunset | 6:11 am / 8:19 pm | 6:37 am / 7:41 pm |
| Daylight | 14.1 h | 13.1 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Pacific Time).
A typical August day
- 6 am59°Fdew point 54°F
- 9 am71°Fdew point 54°F
- Noon82°Fdew point 53°F
- 3 pm88°Fdew point 52°F
- 6 pm79°Fdew point 54°F
- 9 pm66°Fdew point 53°F
NOAA hourly normals (local standard time) from Travis AFB (19 mi away); average wind 17 mph; clear or few clouds in 91% of daytime hours, mostly cloudy or overcast in 5%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F13 of 31
- Hot dayshigh 90°F or more6 of 31
- Muggy daysdaily mean dew point 65°F or more0 of 31
- Wet daysat least 0.01 in of rain or melted snow0 of 31
- Notable rainat least 0.10 in0 of 31
- Freezing nightslow 32°F or below0 of 31
Average days per August, counted from daily records for each year 1991-2020.
Rain in August
Normal precipitation is 0.06 in; a dry August brings about 0.0 in and a wet one about 0.0 in (25th and 75th percentiles). Days with half an inch or more are rare.
How August varies from year to year
- Warmest August, 1991-20202020: average high 88°F
- Coolest August2011: average high 79°F
- Wettest August1997: 0.8 in
- Driest August1992: no measurable precipitation
- Highest reading107°F (August 15, 2020)
- Lowest reading43°F (August 12, 1993)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
August compared with July and September
| July | August | September | |
|---|---|---|---|
| Normal high | 83°F | 84°F | 84°F |
| Normal low | 56°F | 56°F | 53°F |
| Wet days | 0 | 0 | 1 |
| Comfortable days | 13 | 13 | 11 |
| Daylight | 14.5 h | 13.6 h | 12.4 h |
Highs change by +1°F from July and 0°F into September.
Nearby alternatives in August
- Warmer: Fairfield, CA14 mi · high 89°F · 0 wet days
- Cooler: San Francisco, CA37 mi · high 68°F · 1 wet day
How Napa ranks in August
- Normal high235th warmest of 378 cities; 40th of 60 in California
- Wet days21st driest of 378
- Comfortable days41st most of 341
What to pack for Napa in August
- Layers – afternoons near 84°F but nights near 56°F
Heating and cooling
August has 4 heating degree days and 147 cooling degree days (base 65°F), 5% of the year's total heating and cooling demand.
Questions
How hot is Napa in August?
The normal high is 84°F and the normal low is 56°F. From 1991 to 2020 the hottest August reading was 107°F (August 15, 2020).
Does it rain a lot in Napa in August?
About 0 days in August have at least 0.01 in of precipitation, and the normal total is 0.06 in. The wettest August in 1991-2020 was in 1997 (0.8 in); the driest was in 1992, with no measurable precipitation.
Is August a good time to visit Napa?
August ranks 6th of 12 months on our comfort score for Napa (69 out of 100). It has about 13 comfortable days and about 6 days at 90°F or hotter. The best month is May.
Where the numbers come from
- Temperature, rain, snowfall and frost dates: Napa State Hospital (USC00046074), 1.8 mi SE of the city center, 35 ft . NOAA normals and daily records, 1991-2020.
- Snow depth: Fairfield (USC00042934), 12 mi E of the city center, 40 ft . NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour and cloud cover: Travis AFB (USW00023202), 19 mi E of the city center, 59 ft . NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Napa County Airport (724955-93227), 6.2 mi S of the city center, 15 ft . Hourly observations, 1991-2020.