St. Helena, CA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for St. Helena, a city in Napa County, California.
This Afternoon
85°F
Sunny
Sunny, with a high near 85. West wind around 5 mph.
7-day forecast for St. Helena
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 85°F | Sunny | 5 mph W | 0% |
| Tonight | 54°F | Mostly Clear then Patchy Fog | 0 to 5 mph WNW | 0% |
| Saturday | 90°F | Sunny | 0 to 5 mph SW | 0% |
| Saturday Night | 54°F | Mostly Cloudy then Patchy Fog | 2 mph NW | 0% |
| Sunday | 84°F | Patchy Fog then Mostly Cloudy | 2 mph SW | 0% |
| Sunday Night | 53°F | Mostly Cloudy then Areas Of Fog | 2 mph WNW | 0% |
| Monday | 86°F | Areas Of Fog then Mostly Sunny | 0 to 3 mph SW | 0% |
| Monday Night | 52°F | Mostly Clear then Areas Of Fog | 0 to 3 mph SW | 0% |
| Tuesday | 88°F | Areas Of Fog then Sunny | 2 mph WSW | 0% |
| Tuesday Night | 55°F | Mostly Clear | 2 mph WNW | 0% |
| Wednesday | 94°F | Sunny | 2 mph NNW | 0% |
| Wednesday Night | 58°F | Mostly Clear | 2 mph WNW | 0% |
| Thursday | 95°F | Sunny | 0 to 3 mph SW | 0% |
| Thursday Night | 57°F | Partly Cloudy | 0 to 3 mph WNW | 0% |
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.