Napa County Weather in May
Average highs run from 75°F on May 1 to 82°F on May 31, and lows from 48°F to 53°F. Normal precipitation for the month is 1.31 in over about 3 wet days.
May day by day
The normal high and low for each date, and the record, in °F.
- Normal low
- Normal high
- Record high
- Record low
May at a glance
- Average high
- 78°F
- Average low
- 51°F
- Precipitation
- 1.31 in
- Record high
- 101°FMay 15, 2008
- Record low
- 31°FMay 23, 2010
- Chance of a freeze
- 0%
- Days of 90°F or more
- 3.8
- Daylight
- 13 h 49 min to 14 h 40 min
- Cloud cover
- 41%
- Humidity
- 70%
- Dew point
- 48°F
- Wind
- 6.9 mph
Every day of the month
A wet day has at least 0.01 inch of precipitation.
| Date | Normal high | Normal low | Record high | Record low | Chance wet |
|---|---|---|---|---|---|
| May 1 | 75°F | 48°F | 91°F 2017 | 34°F 2008 | 14% |
| May 2 | 75°F | 48°F | 93°F 2017 | 37°F 2002 | 14% |
| May 3 | 75°F | 49°F | 93°F 2021 | 36°F 2008 | 13% |
| May 4 | 76°F | 49°F | 85°F 2021 | 36°F 1999 | 13% |
| May 5 | 76°F | 49°F | 85°F 2025 | 37°F 2003 | 13% |
| May 6 | 76°F | 49°F | 90°F 2007 | 38°F 2003 | 13% |
| May 7 | 76°F | 49°F | 93°F 2001 | 37°F 2010 | 12% |
| May 8 | 76°F | 49°F | 92°F 2001 | 36°F 1999 | 12% |
| May 9 | 77°F | 50°F | 87°F 2025 | 33°F 2003 | 12% |
| May 10 | 77°F | 50°F | 94°F 2021 | 32°F 2022 | 12% |
| May 11 | 77°F | 50°F | 84°F 2018 | 32°F 2022 | 12% |
| May 12 | 77°F | 50°F | 84°F 2014 | 37°F 2002 | 11% |
| May 13 | 77°F | 50°F | 89°F 2014 | 37°F 1999 | 11% |
| May 14 | 78°F | 50°F | 95°F 2008 | 39°F 2017 | 11% |
| May 15 | 78°F | 50°F | 101°F 2008 | 34°F 1999 | 11% |
| May 16 | 78°F | 51°F | 95°F 2008 | 37°F 1999 | 11% |
| May 17 | 78°F | 51°F | 95°F 2009 | 41°F 1999 | 10% |
| May 18 | 79°F | 51°F | 91°F 2022 | 39°F 2013 | 10% |
| May 19 | 79°F | 51°F | 89°F 2026 | 40°F 2003 | 10% |
| May 20 | 79°F | 51°F | 91°F 2013 | 38°F 2021 | 10% |
| May 21 | 79°F | 51°F | 96°F 2000 | 37°F 2021 | 9% |
| May 22 | 79°F | 51°F | 92°F 2000 | 35°F 2010 | 9% |
| May 23 | 80°F | 52°F | 91°F 2000 | 31°F 2010 | 9% |
| May 24 | 80°F | 52°F | 93°F 2022 | 38°F 2011 | 9% |
| May 25 | 80°F | 52°F | 94°F 2020 | 42°F 2001 | 8% |
| May 26 | 80°F | 52°F | 98°F 2020 | 40°F 1998 | 8% |
| May 27 | 81°F | 52°F | 89°F 2020 | 42°F 2012 | 8% |
| May 28 | 81°F | 52°F | 92°F 2003 | 35°F 2010 | 7% |
| May 29 | 81°F | 52°F | 87°F 2002 | 38°F 2006 | 7% |
| May 30 | 81°F | 53°F | 100°F 2001 | 40°F 2013 | 7% |
| May 31 | 82°F | 53°F | 96°F 2001 | 41°F 2011 | 6% |
Chance of rain
- Chance of a wet day
Sunrise and sunset
Times for 2026, local time (PDT).
- May 1
- sunrise 6:12 AM, sunset 8:01 PM
- May 31
- sunrise 5:47 AM, sunset 8:27 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00047643 (Saint Helena), public domain. Records: NOAA GHCN-Daily, station USW00093227, every year on file, quality-flagged values removed. Cloud, humidity, wind and sunshine: NASA POWER (MERRA-2, CERES and GEWEX SRB), 1991-2020. The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center's Prediction Of Worldwide Energy Resources (POWER) project funded through the NASA Earth Science Division: POWER Daily API v2, accessed 2026-09-24. Sun and moon: computed with the NOAA solar equations and Meeus.