St. Helena, California Weather
Summer heat deepens across the valleys. Day 15 of summer. Read this microseason across nine climate regions →
St. Helena weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJul 5Foggy——85°55°—
- MondayJul 6Foggy——86°49°+1°
- TuesdayJul 7Foggy——91°50°+5°
- WednesdayJul 8Clear——96°52°+5°
- ThursdayJul 9Clear——98°56°+2°
- FridayJul 10Overcast——100°54°+2°
- SaturdayJul 11Overcast——99°59°-1°
AQI 29 (Good), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 5.0 µg/m³ (AQI 28) with a 0.74 fine-to-coarse ratio and 5 mph wind — combustion smoke trapped in calm air, not road dust.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.
What's driving it
PM × Wind × Precip
PM2.5 at 5.0 µg/m³ (AQI 28) with a 0.74 fine-to-coarse ratio and 5 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.74
- Wind
- light
- Recent rain
- 0h in last 6h
- Pattern
- stagnant smoke
Trends
Seven days of AQI and PM2.5.
Hourly air-quality data from the Copernicus Atmosphere Monitoring Service, charted across the past and next several days. Dashed lines mark the AQI breakpoints at 50 (Good → Moderate) and 100 (Moderate → Unhealthy for Sensitive Groups).
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
- Moonrise
- 11:29 PM
- Moonset
- 11:28 AM
- In sign
- ♓︎ Pisces
Summer heat deepens across the valleys
St. Helena at a glance
- Today vs. normal: 73°F — typical for the season
- Last frost: April 7 (climatological average for this latitude)
- Microseason: Jul 1–5
- Planting window: Harvest early potatoes. Begin drying onions on the surface.
16-Day Forecast — St. Helena
- Sun85°55°0%
- Mon86°49°0%
- Tue91°50°0%
- Wed96°52°0%
- Thu98°56°0%
- Fri100°54°0%
- Sat99°59°1%
- Sun90°63°1%
- Mon98°66°2%
- Tue106°63°4%
- Wed104°62°1%
- Thu104°59°1%
- Fri107°65°3%
- Sat103°61°3%
- Sun100°57°0%
- Mon99°54°3%
Forecast data from Open-Meteo (CC BY 4.0).
Right now in the garden
Peak growing season
As of July 5, the growing season is at its peak — frost is months away. Continue succession-planting beans and summer squash. Start fall brassicas (broccoli, cabbage, kale) from seed indoors for transplanting in late summer.
ZIP codes in St. Helena
- 94574