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
58°F
Light Rain
Rain before 5pm, then a chance of rain and patchy fog. Cloudy. High near 58, with temperatures falling to around 56 in the afternoon. East wind around 3 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch possible.
7-day forecast for St. Helena
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 58°F | Light Rain | 3 mph E | 92% |
| Tonight | 43°F | Chance Light Rain | 3 mph NNW | 47% |
| Wednesday | 69°F | Patchy Fog then Sunny | 3 mph NW | 1% |
| Wednesday Night | 42°F | Partly Cloudy then Patchy Fog | 2 mph NW | 0% |
| Thursday | 74°F | Patchy Fog then Sunny | 2 mph N | 0% |
| Thursday Night | 44°F | Mostly Clear | 1 mph N | 0% |
| Friday | 76°F | Sunny | 1 mph N | 0% |
| Friday Night | 45°F | Mostly Clear | 0 mph | 0% |
| Saturday | 76°F | Sunny | 1 mph NNE | 0% |
| Saturday Night | 45°F | Mostly Clear | 1 mph N | 0% |
| Sunday | 75°F | Mostly Sunny | 2 mph N | 0% |
| Sunday Night | 46°F | Mostly Cloudy | 0 mph | 0% |
| Monday | 73°F | Patchy Fog then Partly Sunny | 1 mph WNW | 2% |
| Monday Night | 45°F | Mostly Cloudy | 0 mph | 3% |
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.