St. Helena, California

Last updated: 2:37 PM CDT  ·  Refresh
27°C
Feels like 24°
Clear
▲ 29°  /  ▼ 11°
Wind
5 mph N
Humidity
26%
Dew Point
5°
Pressure
29.27 inHg
Visibility
10 mi
UV Index
9.7
Cloud Cover
1%
Sunrise
5:47 AM
Sunset
8:38 PM
Drag to pan · double-click to forecast a point
WeatherAI™ Analysis

WeatherAI Analysis: St. Helena is currently clear at 27°C. Dry conditions are expected through the next 24 hours. Sunrise: 5:47AM · Sunset: 8:38PM.

Alerts

No active alerts for this location.
27 AQI · Good Dominant: O3 Air Quality
Hourly Forecast · Next 24 Hours
Now
27°
3%
1 PM
28°
3%
2 PM
28°
3%
3 PM
28°
3%
4 PM
27°
3%
5 PM
29°
3%
6 PM
28°
3%
7 PM
27°
3%
8 PM
24°
3%
9 PM
22°
3%
10 PM
20°
3%
11 PM
19°
3%
12 AM
18°
3%
1 AM
16°
3%
2 AM
15°
3%
3 AM
14°
3%
4 AM
14°
3%
5 AM
11°
3%
6 AM
12°
3%
7 AM
13°
3%
8 AM
14°
3%
9 AM
18°
3%
10 AM
19°
3%
11 AM
21°
3%
7-Day Forecast
Today
29° 11°
Clear.
Mon
30° 11°
Mostly Clear.
Tue
28° 11°
Clear.
Wed
28° 9°
Mostly Clear.
Thu
28° 9°
Clear.
Fri
30° 9°
Clear.
Sat
32° 11°
Clear.
TimeTempConditionsPrecipWindHumidity
Now 27° Clear 3% 5 mph N 26%
1 PM 28° Clear 3% 4 mph N 21%
2 PM 28° Clear 3% 5 mph WNW 24%
3 PM 28° Clear 3% 9 mph W 26%
4 PM 27° Clear 3% 11 mph W 28%
5 PM 29° Clear 3% 11 mph W 30%
6 PM 28° Clear 3% 10 mph W 34%
7 PM 27° Clear 3% 9 mph WNW 39%
8 PM 24° Clear 3% 7 mph WNW 45%
9 PM 22° Clear 3% 5 mph WNW 52%
10 PM 20° Clear 3% 3 mph WNW 58%
11 PM 19° Clear 3% 3 mph WNW 62%
12 AM 18° Clear 3% 3 mph WNW 64%
1 AM 16° Clear 3% 2 mph WNW 65%
2 AM 15° Clear 3% 2 mph NW 67%
3 AM 14° Clear 3% 2 mph NNW 67%
4 AM 14° Mostly Clear 3% 2 mph N 68%
5 AM 11° Mostly Clear 3% 2 mph N 66%
6 AM 12° Mostly Clear 3% 2 mph NNE 61%
7 AM 13° Mostly Clear 3% 2 mph NE 57%
8 AM 14° Mostly Clear 3% 2 mph NE 52%
9 AM 18° Clear 3% 3 mph NE 46%
10 AM 19° Clear 3% 3 mph NE 40%
11 AM 21° Clear 3% 3 mph NE 36%
15-Day Forecast
Today
6/28
Clear
3%
11°
29°
Mon
6/29
Mostly Clear
3%
11°
30°
Tue
6/30
Clear
3%
11°
28°
Wed
7/1
Mostly Clear
3%
9°
28°
Thu
7/2
Clear
3%
9°
28°
Fri
7/3
Clear
3%
9°
30°
Sat
7/4
Clear
3%
11°
32°
Sun
7/5
Clear
3%
11°
31°
Mon
7/6
Clear
3%
11°
31°
Tue
7/7
Clear
3%
11°
33°
Wed
7/8
Clear
3%
12°
33°
Thu
7/9
Clear
3%
12°
34°
Fri
7/10
Clear
3%
12°
34°
Sat
7/11
Clear
3%
13°
34°
Sun
7/12
Clear
3%
13°
34°
27
Good
U.S. Air Quality Index · Dominant: O3
50 100 150 200

Air quality is satisfactory and poses little or no health risk.

Pollutant Breakdown · Today
PM2.5
Fine particulate matter
12 AQI 2.2 µg/m³
O3
Ground-level ozone
Dominant
27 AQI 29 ppb
3-Day Outlook
DayAQICategoryO₃PM2.5
Mon 27 Good 27 12
Tue 24 Good 24 16
Wed 31 Good 31 26
About the Air Quality Index
0–50 Good
51–100 Moderate
101–150 Unhealthy for Sensitive Groups
151–200 Unhealthy
201–300 Very Unhealthy
301–500 Hazardous

The U.S. AQI runs 0–500. The overall value equals the highest individual pollutant sub-index, and the dominant pollutant is the one driving it. PM2.5 (fine particles) is reported in µg/m³ and ozone (O3) in ppb. Forecast source: NWS NAQFC.

1000850700500400300250200150100 -40-30-20-10010203040 0.41247101624 LCLLFCEL0°C Temperature (°C) Pressure (hPa)
Temp Dewpoint Parcel (SB) CAPE CIN Dry adiabat Moist adiabat Mixing ratio
RAP
Valid Sun Jun 28, 18:00'Z' · F0 · 130 (13 km CONUS/NA)
Hodograph · kt
10 20 30 40 50 60 70 80 SM
0–1 1–3 3–6 6–9 km
Instability
SBCAPE156 J/kg
MLCAPE22 J/kg
MUCAPE156 J/kg
SBCIN0 J/kg
MLCIN0 J/kg
Lifted Index7.1
Kinematics
0–6 km Shear68 kt
0–1 km Shear6 kt
Eff. Shear6 kt
0–1 km SRH-29
0–3 km SRH-92
Eff. SRH-92
Storm Motion309° @ 27 kt
0–1 km EHI-0.0
Composite Parameters
Sig. Tornado-0.0
STP (eff)0.0
Supercell0.0
K-Index-2.5
Thermo & Levels
PWAT0.49 in
0–3 km LR8.2 °C/km
700–500 LR5.0 °C/km
Total Totals31.9
LCL724 hPa
LFC991 hPa
EL761 hPa
Freezing Lvl10,801 ft