SEA-TAC, WASHINGTON

Average Temperature

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		11.8		5.7		6.4		8.6		10.6		13.8		16.6		19.2		19.4		16.4		11.6		7.7		4.8

Average High Temperature

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		16.1		8.7		10.3		12.6		15.2		18.6		21.6		24.7		25.1		21.8		15.7		11.1		7.7

Average Low Temperature

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		7.4		2.7		2.5		4.5		6		8.9		11.6		13.7		13.8		11.1		7.4		4.4		1.9

Highest Recorded Temperature

Years on Record: 68

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		39.4		17.8		21.1		25.6		29.4		33.9		35.6		39.4		37.2		36.7		31.7		23.3		17.8

Lowest Recorded Temperature

Years on Record: 68

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		-17.8		-17.8		-17.2		-11.7		-1.7		-2.2		3.3		6.1		6.7		1.7		-2.2		-14.4		-14.4

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		0.1		---		---		---		---		---		---		0.1		---		---		---		---		---

Average Number of Days Above 90F/32C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		2.1		---		---		---		---		---		0.3		1.3		0.5		0.1		---		---		---

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		26		---		---		---		0.1		1		3.9		9		9.3		2.7		---		---		---

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		93.5		---		---		0.4		2.1		6.9		14.1		25.4		27.1		16.1		1.3		0.1		---

Average Number of Days Above 65F/18C

Years on Record: 48

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		127		---		---		1		5		13		21		29		29		22		6		---		---

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		178.6		0.3		0.7		5		11.7		24.7		28.2		30.9		31		29.2		15.4		1.5		0.2

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		290		11.2		15.5		24.8		28.4		31		30		31		31		30		30.4		19.8		7

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		356.8		28.1		27.7		30.8		30		31		30		31		31		30		31		29.3		26.7

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		364.9		31		28		31		30		31		30		30.9		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		353.5		31		28		31		30		30.9		29.6		26.5		25.2		29.3		31		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		240.7		30.7		28		30.6		28.8		20.8		6.5		0.6		0.8		8.9		24.9		29		31

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		107.3		21.2		19.6		14.9		7.8		1		---		---		---		---		5.3		13.8		23.8

Average Number of Days Below 32F/0C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		25.7		6.6		5.7		1.8		0.1		---		---		---		---		---		0.5		3.5		7.7

Average Number of Days Below 20F/-6C

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		1.5		0.3		---		---		---		---		---		---		---		---		---		0.2		1

Average Precipitation

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
mm		1018.5		144.8		109.2		101.6		78.7		53.3		40.6		22.9		22.9		43.2		96.5		165.1		137.2

Average Precipitable Water

Years on Record: 20

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
cm.		1.6		1.2		1.1		1.2		1.3		1.6		1.9		2.3		2.3		2		1.7		1.4		1.2

Average Number of Rainy Days

Years on Record: 49

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		154		18		16		17		14		10		9		5		6		9		13		18		19

Average Number of Days With Thunderstorms

Years on Record: 48

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

Most Rain Reported in a Month

Years on Record: 48

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
mm		1390		320		230		210		160		120		90		60		110		140		190		270		290

Least Recorded Rainfall

Years on Record: 48

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
mm		600		10		---		10		---		---		---		---		---		---		---		10		30

Average Snowfall

Years on Record: 49

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
cm		29		12		4		3		---		---		---		---		---		---		---		3		6

Average Relative Humidity

Years on Record: 20

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
%		75.2		80.9		76.7		76.7		73.7		71.4		69.9		67.1		69		73.8		80.5		82.5		80.9

Average Morning Relative Humidity

Years on Record: 48

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
%		83		83		83		84		83		80		79		79		83		88		88		86		85

Average Evening Relative Humidity

Years on Record: 48

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
%		62		75		69		63		57		54		53		49		51		56		68		76		79

Average Dew Point

Years on Record: 48

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
C		6		---		1		2		3		6		8		11		11		10		7		3		1

Heating Degree Days

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		4533		704		601		547		418		259		119		34		24		123		377		573		753

Cooling Degree Days

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		218		---		---		---		---		5		25		82		84		21		---		---		---

Growing Degree Days

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		2194		5		2		26		70		214		356		513		525		348		114		19		2

Average Length of Day

Years on Record: 30

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Hours		12.8		9.6		10.9		12.5		14.2		15.8		16.6		16.1		14.7		13		11.3		9.9		9.1

Average Number of Days With Fog

Years on Record: 48

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		164		18		15		13		10		8		8		8		11		16		19		19		19

Average Number of Clear Days

Years on Record: 49

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		58		3		3		3		3		4		5		10		9		8		4		3		2

Average Possibility of Sunshine

Years on Record: 27

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
%		47		26		39		49		52		55		56		64		65		61		43		28		22

Average Number of Cloudy Days

Years on Record: 49

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		226		24		21		22		20		18		17		11		12		13		20		23		25

Average Number of Partly Cloudy Days

Years on Record: 49

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Days		81		4		4		6		7		9		8		10		10		9		7		4		4

Average Total Sky Cover

Years on Record: 20

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
%		69		80.2		71.3		76.1		73.2		69.8		68.4		51.3		51.8		53.4		70.5		79.8		81

Average Opaque Sky Cover

Years on Record: 20

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
%		64.1		75.9		66.3		71.2		67.5		64.2		62.9		48.1		47.2		48		66.1		75.7		76.3

Highest Reported Hourly Wind Speed

Years on Record: 44

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
km/h		106.2		75.6		82.1		70.8		61.2		51.5		57.9		41.8		46.7		57.9		62.8		106.2		83.7

Average Daily Solar Radiation - Global

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		12.8		4.4		7.6		11.3		15.7		18.6		20.7		22.9		20.3		15.3		9.1		4.9		3.7

Average Daily Solar Radiation - Diffuse

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		6		2.7		4		5.9		7.7		9		9.5		9.2		8		6.7		4.5		3		2.3

Average Daily Solar Radiation - Reflected

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		13.9		7.1		10.9		13.5		16.2		17.1		18		20.4		20.2		17.8		12.3		7.8		6.1

Average Daily Solar Radiation - Direct

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		13.4		6.2		9.8		11.6		14.5		16.2		18.4		22.5		21.3		17.1		11.5		6.7		5.5

Maximum Daily Solar Radiation - Global

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		12.8		4.4		7.6		11.3		15.7		18.6		20.7		22.9		20.3		15.3		9.1		4.9		3.7

Maximum Daily Solar Radiation - Diffuse

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		6.4		3.1		4.4		6.5		7.7		9.1		9.6		10		8.3		7.4		5.3		3.6		2.6

Maximum Daily Solar Radiation - Reflected

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		16.9		9.5		12.3		17.6		19.1		22		20.9		23.9		22.3		21.2		15.7		10.7		7.3

Maximum Daily Solar Radiation - Direct

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		17.5		8.3		11.4		16.4		19.3		24.9		24.1		27.6		24.2		21.4		15.3		9.7		6.8

Minimum Daily Solar Radiation - Global

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		10.7		3.8		5.7		9.4		13.4		14.9		17.1		19		17.9		12.5		7.4		4.1		3.3

Minimum Daily Solar Radiation - Diffuse

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		5.7		2.4		3.4		5.6		7.5		8.8		9.3		9		7.9		6.2		4		2.6		2.1

Minimum Daily Solar Radiation - Reflected

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		11.4		5.9		7.8		10.8		13.5		13.5		14.9		16.9		17.6		14.1		9.7		6.2		5.3

Minimum Daily Solar Radiation - Direct

Years on Record: 22

		ANNUAL		JAN		FEB		MAR		APR		MAY		JUN		JUL		AUG		SEP		OCT		NOV		DEC
Mj/m2		9.7		5		6.6		8.3		10.4		10		12.2		16		17.1		12.6		8.7		5.1		4.6