Severe Thunderstorm Watch 8:00 PM

St. Helena, California

Last updated: 5:20 PM CDT  ·  Refresh
29°C
Feels like 28°
Partly Cloudy
▲ 32°  /  ▼ 9°
Wind
7 mph W
Humidity
29%
Dew Point
11°
Pressure
29.39 inHg
Visibility
10 mi
UV Index
7.2
Cloud Cover
57%
Sunrise
6:28 AM
Sunset
7:55 PM
Drag to pan · double-click to forecast a point
WeatherAI™ Analysis

WeatherAI Analysis: St. Helena is currently partly cloudy at 29°C. Dry conditions are expected through the next 24 hours. Sunrise: 6:28AM · Sunset: 7:55PM.

Alerts

Severe Thunderstorm Watch
Expires 8:00 PM
29 AQI · Good Dominant: O3 Air Quality
Hourly Forecast · Next 24 Hours
Now
29°
3%
4 PM
28°
3%
5 PM
32°
3%
6 PM
29°
3%
7 PM
27°
3%
8 PM
23°
3%
9 PM
20°
3%
10 PM
19°
3%
11 PM
18°
3%
12 AM
17°
3%
1 AM
14°
3%
2 AM
14°
3%
3 AM
13°
3%
4 AM
13°
3%
5 AM
9°
3%
6 AM
10°
3%
7 AM
11°
3%
8 AM
13°
3%
9 AM
16°
3%
10 AM
21°
3%
11 AM
23°
3%
12 PM
24°
3%
1 PM
28°
3%
2 PM
28°
3%
7-Day Forecast
Today
32° 9°
Partly Cloudy.
Sat
32° 9°
Mostly Clear.
Sun
33° 12°
Partly Cloudy.
Mon
31° 9°
Mostly Clear.
Tue
26° 9°
Mostly Cloudy.
Wed
30° 8°
Mostly Clear.
Thu
31° 12°
Clear.
TimeTempConditionsPrecipWindHumidity
Now 29° Partly Cloudy 3% 7 mph W 29%
4 PM 28° Mostly Cloudy 3% 8 mph W 30%
5 PM 32° Partly Cloudy 3% 8 mph W 33%
6 PM 29° Partly Cloudy 3% 7 mph W 47%
7 PM 27° Mostly Clear 3% 6 mph W 55%
8 PM 23° Clear 3% 4 mph W 63%
9 PM 20° Clear 3% 4 mph W 70%
10 PM 19° Clear 3% 4 mph WSW 74%
11 PM 18° Clear 3% 4 mph WSW 78%
12 AM 17° Mostly Clear 3% 4 mph W 78%
1 AM 14° Mostly Clear 3% 4 mph W 78%
2 AM 14° Mostly Clear 3% 4 mph W 77%
3 AM 13° Partly Cloudy 3% 4 mph W 76%
4 AM 13° Partly Cloudy 3% 4 mph W 76%
5 AM 9° Partly Cloudy 3% 4 mph W 74%
6 AM 10° Partly Cloudy 3% 3 mph W 69%
7 AM 11° Partly Cloudy 3% 3 mph WNW 64%
8 AM 13° Mostly Clear 3% 3 mph WNW 56%
9 AM 16° Mostly Clear 3% 2 mph W 44%
10 AM 21° Mostly Clear 3% 2 mph W 34%
11 AM 23° Mostly Clear 3% 3 mph WSW 28%
12 PM 24° Mostly Clear 3% 3 mph WSW 25%
1 PM 28° Mostly Clear 3% 4 mph WSW 23%
2 PM 28° Mostly Clear 3% 5 mph WSW 21%
15-Day Forecast
Today
8/21
Partly Cloudy
3%
9°
32°
Sat
8/22
Mostly Clear
3%
9°
32°
Sun
8/23
Partly Cloudy
3%
12°
33°
Mon
8/24
Mostly Clear
3%
9°
31°
Tue
8/25
Mostly Cloudy
3%
9°
26°
Wed
8/26
Mostly Clear
3%
8°
30°
Thu
8/27
Clear
3%
12°
31°
Fri
8/28
Partly Cloudy
3%
9°
30°
Sat
8/29
Clear
3%
11°
29°
Sun
8/30
Clear
3%
9°
33°
Mon
8/31
Clear
3%
9°
29°
Tue
9/1
Clear
3%
11°
29°
Wed
9/2
Clear
3%
12°
29°
Thu
9/3
Clear
3%
12°
31°
Fri
9/4
Clear
60%
13°
32°
29
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
21 AQI 3.7 µg/m³
O3
Ground-level ozone
Dominant
29 AQI 32 ppb
3-Day Outlook
DayAQICategoryO₃PM2.5
Sat 29 Good 29 21
Sun 26 Good 26 15
Mon 30 Good 30 11
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 Fri Aug 21, 21:00'Z' · F0 · 130 (13 km CONUS/NA)
Hodograph · kt
10 20 30 40 50 60 70 SM
0–1 1–3 3–6 6–9 km
Instability
SBCAPE40 J/kg
MLCAPE28 J/kg
MUCAPE0 J/kg
SBCIN0 J/kg
MLCIN-0 J/kg
Lifted Index3.0
Kinematics
0–6 km Shear38 kt
0–1 km Shear7 kt
Eff. Shear—
0–1 km SRH-5
0–3 km SRH104
Eff. SRH—
Storm Motion238° @ 31 kt
0–1 km EHI-0.0
Composite Parameters
Sig. Tornado0.0
STP (eff)—
Supercell—
K-Index14.3
Thermo & Levels
PWAT0.96 in
0–3 km LR6.1 °C/km
700–500 LR7.5 °C/km
Total Totals35.5
LCL764 hPa
LFC995 hPa
EL928 hPa
Freezing Lvl14,692 ft