ST. HELENA, CALIFORNIA

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Elevation: 52 meters Latitude: 38 26N Longitude: 122 25W

WEATHER

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CURRENT CONDITIONS

Sunrise/Set

05:54 am

08:17 pm
Local Time
1:04 pm PDT
18 May, 2024

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MONTHLY - ALL WEATHER AVERAGES [ Show Summary ]

[ °F ] °C

TEMPERATURE

Average Temperature

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		15.1		8.6		10.4		12.3		13.9		17.3		19.8		20.7		20.8		19.8		16.8		12		8.6

Average High Temperature

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		23.1		14.5		17.1		19.3		21.9		26.1		29.1		29.9		30.3		29.3		25.8		19.2		14.8

Average Low Temperature

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		7.1		2.6		3.8		5.3		5.9		8.6		10.4		11.5		11.3		10.3		7.7		4.8		2.4

Highest Recorded Temperature

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		28.9		15.6		18.5		20.4		21.5		24.4		27.6		24.8		25.6		28.9		24.8		20.9		16.4

Lowest Recorded Temperature

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		4.3		4.3		5.8		6.4		6.9		9.5		11.6		12.4		11.9		12.4		10.8		7.2		4.4

Average Number of Days Above 100F/38C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		3.5		---		---		---		---		---		0.7		0.9		0.5		1.5		---		---		---

Average Number of Days Above 90F/32C

Years on Record: 76

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		31.9		---		---		0.4		0.8		2		4.2		7.4		7.6		6.5		3.1		---		---

Average Number of Days Above 80F/26C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		125.4		---		---		1.9		3.6		11.9		20.9		26.6		25.1		20.4		14.3		0.7		---

Average Number of Days Above 70F/21C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		216.7		1.7		3.3		10		18.1		27.6		29.7		31		30.8		29.7		25		9.5		0.3

Average Number of Days Above 60F/15C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		300.4		11.3		18.1		24.7		28.1		30.8		30		31		31		30		30.5		24.2		10.7

Average Number of Days Above 50F/10C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		360.6		28.4		27.7		30.8		29.8		30.8		30		31		31		30		31		29.7		30.3

Average Number of Days Above 40F/4C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		365		31		28		31		30		31		30		31		31		30		31		30		31

Average Number of Days Below 70F/21C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		365		31		28		31		30		31		30		31		31		30		31		30		31

Average Number of Days Below 60F/15C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		362.9		31		28		31		30		30.8		29.8		30.6		30.5		29.5		30.6		30		31

Average Number of Days Below 50F/10C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		262.2		30.4		27.3		28.7		27.9		22.4		13.2		6.2		7.1		14		26.4		28		30.5

Average Number of Days Below 40F/4C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		99.2		20.9		17.3		13.1		9.5		0.8		---		---		---		---		2.4		14.7		20.7

Average Number of Days Below 32F/0C

Years on Record: 76

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		60.2		12.9		8.8		7.6		3.4		0.8		0.2		---		---		0.4		4		7.9		14.2

PRECIPITATION

Average Precipitation

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
mm		858.5		160		172.7		121.9		48.3		30.5		5.1		---		2.5		7.6		38.1		101.6		172.7

Average Number of Days With Precipitation

Years on Record: 76

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		60		11		9		9		5		3		1		---		1		1		4		7		9

Most Reported Precipitation in a Month

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
mm		385		316		385		250		105		76		23		30		32		39		108		246		226

Least Reported Precipitation in a Month

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
mm		---		8		5		1		---		---		---		---		---		---		---		2		---

Most Precipitation Reported in a Day

Years on Record: 76

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
mm		166.4		148.6		117.3		102.6		67.8		20.3		29.2		30		8.1		68.6		126.5		101.6		166.4

Avg. No. of Days w/Precip. Above 0.2in/5mm

Years on Record: 76

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		45		9		7		7		3		1		1		---		---		1		3		6		7

Avg. # of Days w/Precip. Above 0.4in/10mm

Years on Record: 76

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		20		5		4		3		1		---		---		---		---		---		1		3		3

Avg. No. of Days w/Precip. Above 1in/25mm

Years on Record: 76

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		10		3		2		1		---		---		---		---		---		---		1		1		2

PRECIPITATION - SNOW

Average Snowfall

Years on Record: 76

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
cm		0.2		0.2		---		---		---		---		---		---		---		---		---		---		---

Most Snow Reported in a Month

Years on Record: 76

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
cm		7.6		7.6		---		---		---		---		---		---		---		---		---		---		---

DEGREE DAYS

Heating Degree Days

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		2688		547		398		339		246		96		21		6		5		28		117		343		542

Cooling Degree Days

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		567		---		---		3		8		38		99		139		143		107		28		1		---

Growing Degree Days

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		3639		21		57		151		215		408		528		598		603		529		377		130		22

SKY CONDITIONS

Average Length of Day

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Hours		12.7		10.3		11.3		12.5		13.7		14.8		15.3		15		14.1		12.8		11.6		10.5		10

SOLAR RADIATION

Average Daily Solar Radiation - Global

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		18.2		7.9		11.4		16.9		22		26.1		28.8		28.3		25.4		20.6		14.9		9.6		7.2

Average Daily Solar Radiation - Diffuse

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		4.6		3		3.8		4.8		5.9		6.5		6.3		6		5.3		4.4		3.6		3		2.6

Average Daily Solar Radiation - Reflected

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		20.2		12.6		15.7		20.5		22.7		23.8		24.7		24.9		24.9		23.8		20.9		15.2		12.2

Average Daily Solar Radiation - Direct

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		24.2		13.3		17		22.4		26.2		30.2		34		33.9		31.9		28.4		23.6		16.7		13

Maximum Daily Solar Radiation - Global

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		18.2		7.9		11.4		16.9		22		26.1		28.8		28.3		25.4		20.6		14.9		9.6		7.2

Maximum Daily Solar Radiation - Diffuse

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		5.4		3.2		4.2		5.7		7		8.5		7.8		7.1		6		5		4.1		3.4		2.8

Maximum Daily Solar Radiation - Reflected

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		23.5		16.4		22.1		26.2		25		26.4		26.3		26.9		26.9		25.9		22.9		19.1		18.4

Maximum Daily Solar Radiation - Direct

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		30.3		18.8		27.2		32.2		31		36.5		38.5		39.4		36.5		32.3		26.7		22.8		22.1

Minimum Daily Solar Radiation - Global

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		15.6		5.7		8		13.9		18.6		19.3		25.3		25.7		23.9		19.3		13.3		8		5.9

Minimum Daily Solar Radiation - Diffuse

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		3.7		2.6		2.6		3.2		5.1		5.2		5.4		4.8		4.3		3.6		3.1		2.4		1.9

Minimum Daily Solar Radiation - Reflected

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		16.6		7.8		9.8		16.1		18.9		17.7		22		22.8		23.4		22		18		11.7		9.2

Minimum Daily Solar Radiation - Direct

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		17.8		6.8		8.3		15.2		18.9		16.7		26.6		28.3		28.3		25.1		19		11.6		8.9

NEARBY - MAP

NEARBY - LIST

Oakville, California (5 mi / 8 km)
Angwin, California (9 mi / 15 km)
Boyes Hot Springs, California (10 mi / 16 km)
Spanish Flat, California (12 mi / 20 km)
Calistoga, California (13 mi / 22 km)

GEOBA.SE

St. Helena, California