St. Helena, CA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for St. Helena, a city in Napa County, California.
Today
100°F
Haze then Sunny
Haze before 8am. Sunny. High near 100, with temperatures falling to around 97 in the afternoon. South southwest wind 0 to 5 mph.
7-day forecast for St. Helena
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 100°F | Haze then Sunny | 0 to 5 mph SSW | 0% |
| Tonight | 55°F | Partly Cloudy then Patchy Fog | 0 to 5 mph WSW | 0% |
| Wednesday | 96°F | Patchy Fog then Mostly Sunny | 0 to 5 mph WSW | 0% |
| Wednesday Night | 54°F | Partly Cloudy then Areas Of Fog | 0 to 5 mph W | 0% |
| Thursday | 94°F | Patchy Fog then Mostly Sunny | 0 to 5 mph WSW | 0% |
| Thursday Night | 55°F | Partly Cloudy | 0 to 5 mph W | 0% |
| Friday | 98°F | Mostly Sunny | 0 to 3 mph SW | 0% |
| Friday Night | 58°F | Mostly Clear | 0 to 3 mph SW | 0% |
| Saturday | 98°F | Sunny | 0 to 3 mph SW | 0% |
| Saturday Night | 59°F | Mostly Clear | 0 to 3 mph WNW | 0% |
| Sunday | 95°F | Sunny | 0 to 5 mph SSW | 0% |
| Sunday Night | 56°F | Mostly Clear then Areas Of Fog | 0 to 5 mph SSW | 0% |
| Monday | 88°F | Areas Of Fog then Sunny | 0 to 5 mph SSW | 0% |
| Monday Night | 53°F | Mostly Clear | 0 to 5 mph SW | 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 Aug 4, 2026.