St. Helena, CA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for St. Helena, a city in Napa County, California.
Overnight
43°F
Patchy Fog
Patchy fog before 5am. Mostly clear, with a low around 43. West southwest wind around 2 mph.
7-day forecast for St. Helena
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 43°F | Patchy Fog | 2 mph WSW | 0% |
| Wednesday | 69°F | Sunny | 3 mph NW | 2% |
| Wednesday Night | 43°F | Mostly Cloudy then Patchy Fog | 2 mph NNW | 2% |
| Thursday | 74°F | Patchy Fog then Mostly Sunny | 2 mph N | 0% |
| Thursday Night | 42°F | Mostly Clear | 1 mph N | 0% |
| Friday | 77°F | Mostly Sunny | 0 mph | 0% |
| Friday Night | 44°F | Mostly Clear | 0 mph | 0% |
| Saturday | 77°F | Sunny | 1 mph NNE | 0% |
| Saturday Night | 44°F | Mostly Clear | 1 mph N | 0% |
| Sunday | 76°F | Mostly Sunny | 2 mph N | 0% |
| Sunday Night | 46°F | Partly Cloudy | 0 mph | 0% |
| Monday | 73°F | Patchy Fog then Partly Sunny | 0 mph | 2% |
| Monday Night | 45°F | Partly Cloudy | 0 mph | 2% |
| Tuesday | 73°F | Patchy Fog then Sunny | 0 mph | 8% |
Forecast source: National Weather Service (api.weather.gov) for St. Helena (38.513, -122.468). Updated through the day.
Growing snapshot for St. Helena
Last spring frost
Apr 7
First fall frost
Dec 5
Growing season
245 days
Hardiness zone
9b
More local growing data for St. Helena: nearby ZIP 94576 weather · frost dates · planting calendar · California frost dates
Nearby towns & communities
American Canyon
Angwin
Deer Park
Moskowite Corner
Napa
Oakville
Rutherford
Silverado Resort
Yountville
Climate data from the nearest NOAA station, Angwin Pacific Union College, Ca (2.5 mi from St. Helena). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.