St. Helena, CA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for St. Helena, a city in Napa County, California.
Tonight
54°F
Partly Cloudy
Partly cloudy, with a low around 54. Wind around 0 mph.
7-day forecast for St. Helena
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 54°F | Partly Cloudy | 0 mph | 0% |
| Saturday | 90°F | Sunny | 0 to 5 mph SW | 0% |
| Saturday Night | 54°F | Mostly Cloudy then Patchy Fog | 0 to 3 mph NW | 0% |
| Sunday | 84°F | Patchy Fog then Mostly Cloudy | 2 mph SSW | 0% |
| Sunday Night | 52°F | Mostly Cloudy then Areas Of Fog | 2 mph WNW | 0% |
| Monday | 86°F | Areas Of Fog then Mostly Sunny | 0 to 5 mph SW | 0% |
| Monday Night | 51°F | Partly Cloudy then Areas Of Fog | 0 to 5 mph WNW | 0% |
| Tuesday | 87°F | Areas Of Fog then Mostly Sunny | 2 mph SW | 0% |
| Tuesday Night | 53°F | Mostly Clear | 2 mph WNW | 0% |
| Wednesday | 93°F | Patchy Fog then Sunny | 2 mph NNW | 0% |
| Wednesday Night | 57°F | Partly Cloudy | 2 mph WNW | 0% |
| Thursday | 94°F | Mostly Sunny | 0 to 3 mph SW | 0% |
| Thursday Night | 56°F | Partly Cloudy | 0 to 3 mph WNW | 0% |
| Friday | 87°F | Mostly Sunny | 0 to 3 mph W | 1% |
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 Sep 19, 2026.