St. Helena, CA Weather - Forecast & Monthly Averages

TEMPERATURE	59
HUMIDITY	100
PRESSURE	101490
WIND COND.	170 18.4

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Weather Quick Facts

The highest monthly average temperature in St. Helena for July is 64.9 degrees
The lowest monthly average temperature in St. Helena for December is 46.1 degrees
The most monthly precipitation in St. Helena occurs in December with 6.9 inches
The air quality index in St. Helena is 19% better than the national average
The pollution index in St. Helena is 190% worse than the national average

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St. Helena Average Temperature

In the event that the weather data was unavailable for this city, estimates based upon nearby cities were used.
Month	Temp. _(min)	Temp. _(max)	Temp. _(avg)	Precipitation
January	36°F	60°F	46°F	6.0"
February	39°F	64°F	50°F	5.7"
March	41°F	67°F	52°F	4.6"
April	43°F	71°F	55°F	2.4"
May	46°F	77°F	60°F	1.1"
June	50°F	83°F	64°F	0.4"
July	52°F	85°F	65°F	0.0"
August	52°F	84°F	64°F	0.0"
September	49°F	85°F	64°F	0.2"
October	46°F	78°F	59°F	2.0"
November	41°F	67°F	52°F	3.2"
December	36°F	59°F	46°F	6.9"

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St. Helena air quality index & pollution index

In the event that the air quality/pollution data was unavailable for this city, estimates based upon nearby cities were used.
Index	St. Helena	California	National
Air quality index	34	55	42
Pollution index	7,898,290	10,473,190	2,726,193

St. Helena air quality

Measurement	Total
Days measured	365
Days with good air quality	346
Days with moderate air quality	18
Days w/ poor A.Q. for sensitive groups	0
Days with unhealthy air quality	1

Air quality details

Pollutant	Total
Arsenic	0.260%
Benzene	0.080%
Carbon Tetrachloride	0.005%
Lead	0.240%
Mercury	0.270%

Average monthly St. Helena temperature with heat index

St. Helena monthly precipitation with daily maximum

St. Helena monthly snow depth with daily maximum

St. Helena monthly wind speed information

Nearby cities with good air quality

City	Population	Air Quality Index	National Avg.
Cotati, CA	7,487	34	32.0%
Penngrove, CA	2,368	34	32.0%
Santa Rosa, CA	178,391	34	32.0%
Angwin, CA	3,415	34	32.0%
Deer Park, CA	772	34	32.0%
St. Helena, CA	6,049	34	32.0%

Cities with similar population

City	Population	Air Quality Index	National Avg.
Amqui, QC	6,049	n/a
Silver Lakes, CA	6,050	89	78.0%
Manchester, WA	6,050	18	64.0%
Willows, CA	6,053	46	8.0%
Metropolis, IL	6,053	44	12.0%
St. Helena, CA	6,049	34	32.0%

Source: The St. Helena, CA weather data displayed above is derived from the NOAA (National Oceanic and Atmospheric). Air quality and pollution data is derived from the EPA (United States Environmental Protection Agency). Air quality and pollution levels measured in a particular area may not be representative of the entire county.