Seattle Climate Records and Averages

Seattle-Tacoma's mild climate is influenced by the Cascade Mountains and to a lesser extent by the Olympic Mountains. The city's climate is characterized by mild temperatures, a pronounced though not sharply defined rainy season and considerable cloudiness, particularly during the winter months. The Cascades are very effective in shielding the Seattle–Tacoma area from the cold, dry continental air during the winter and the hot, dry continental air during the summer months.

The dry season is centered around July and early August with July being the driest month of the year. The rainy season extends from October to March with December normally the wettest month but precipitation is rather evenly distributed through the winter and early spring months, with more than 75 percent of the yearly precipitation falling during the winter wet season. Most of the rainfall in the Seattle area comes from storms common to the middle latitudes.

The occurrence of snow in the Seattle–Tacoma area is extremely variable and usually melts before accumulating to measurable depths. There are winters on record with only a trace of snow but at the other extreme, over 21 inches has fallen in a 24–hour period. Usually, winter storms do not produce snow unless the storm moves in such a way to bring cold air out of Canada directly or with only a short trajectory over water.

Seattle-Tacoma's average first occurrence of 32 degrees Fahrenheit in the fall is November 11 and the average last occurrence in the spring is March 24.

	Monthly Averages			Daily Extremes				Monthly Extremes				Max. Temp.		Min. Temp.
Temperatures in F	Max.	Min.	Avg	High	Date of daily extreme high	Low	Date of daily extreme low	Highest Avg	Year	Lowest Avg	Year	# Days >= 90 F	# Days <= 32 F	# Days <= 32 F	# Days<= 0 F
January	45.0	35.1	40.1	64	20/1981	0	31/1950	47.0	2010	24.9	1950	0.0	1.4	9.8	0.0
February	49.0	36.7	42.9	70	27/1968	1	01/1950	48.7	1977	35.6	1956	0.0	0.2	6.5	0.0
March	52.2	38.2	45.2	78	29/2004	11	04/1955	50.3	1992	39.1	1955	0.0	0.0	3.8	0.0
April	57.4	41.3	49.4	85	30/1976	29	21/1951	53.5	1977	44.5	1955	0.0	0.0	0.4	0.0
May	64.2	46.5	55.3	93	21/1963	28	01/1954	60.4	1958	50.6	1962	0.1	0.0	0.0	0.0
June	69.4	51.4	60.4	96	09/1955	38	12/1952	64.9	1992	55.5	1953	0.5	0.0	0.0	0.0
July	75.3	54.8	65.0	103	29/2009	43	04/1949	69.5	2009	60.0	1955	1.3	0.0	0.0	0.0
August	74.8	55.0	64.9	99	09/1960	44	04/1950	71.1	1967	60.6	1954	0.8	0.0	0.0	0.0
September	69.4	51.5	60.4	98	02/1988	35	27/1972	65.7	1967	55.3	1972	0.2	0.0	0.0	0.0
October	59.3	45.4	52.3	89	01/1987	28	19/1949	56.4	1965	48.6	1949	0.0	0.0	0.4	0.0
November	50.5	39.6	45.1	74	04/1949	6	15/1955	49.4	1965	35.8	1985	0.0	0.2	4.0	0.0
December	45.4	35.9	40.6	64	10/1993	6	30/1968	45.2	1969	35.2	1990	0.0	0.9	8.5	0.0

Annual	59.3	44.3	51.8	103	2009/07/29	0	1950/01/31	54.4	1995	47.9	1955	2.8	2.7	33.3	0.0

Winter	46.5	35.9	41.2	70	1968/02/27	0	1950/01/31	45.0	1992	34.4	1950	0.0	2.5	24.7	0.0
Spring	57.9	42.0	50.0	93	1963/05/21	11	1955/03/04	54.4	1992	44.8	1955	0.1	0.0	4.3	0.0
Summer	73.2	53.7	63.4	103	2009/07/29	38	1952/06/12	66.7	1967	59.0	1954	2.6	0.0	0.0	0.0
Fall	59.7	45.5	52.6	98	1988/09/02	6	1955/11/15	55.9	1967	48.4	1985	0.2	0.2	4.3	0.0

												Total Snowfall
	Avg.	High	Year	Low	Year	1 Day Max.		>= 0.01 in.	>= 0.10 in.	>= 0.50 in.	>= 1.00 in.	Mean	High	Year
	in.	in.	-	in.	-	in.	dd/yyyy or yyyymmdd	# Days	# Days	# Days	# Days	in.	in.	-
January	5.77	12.92	1953	0.58	1985	2.98	18/1986	19	13	4	1	5.0	57.2	1950
February	3.92	9.11	1961	0.35	1993	3.06	08/1996	15	10	2	0	1.7	13.1	1949
March	3.73	8.40	1950	0.57	1965	2.70	05/1972	17	11	2	0	1.3	18.2	1951
April	2.54	6.53	1991	0.33	1956	2.64	04/1991	14	7	1	0	0.1	2.3	1972
May	1.74	3.70	1977	0.12	1992	1.83	29/1969	11	5	1	0	-	-	-
June	1.45	3.82	1964	0.13	1951	1.75	01/1968	9	4	1	0	-	-	-
July	0.74	2.39	1983	0.00	1958	0.85	13/1981	5	2	0	0	-	-	-
August	1.10	4.59	1975	0.01	1974	1.63	18/1975	6	3	1	0	-	-	-
September	1.77	5.95	1978	0.00	1975	1.65	30/1953	9	5	1	0	-	-	-
October	3.48	8.96	2003	0.31	1987	5.02	20/2003	13	8	2	0	0.0	2.0	1971
November	6.15	15.63	2006	0.74	1976	3.41	20/1959	18	13	4	1	0.9	17.5	1985
December	5.81	11.85	1979	1.37	1978	3.77	03/2007	19	13	4	1	2.8	22.1	1968

Annual	38.19	55.14	1950	23.78	1952	5.02	2003/10/20	155	94	22	5	11.8	60.6	1950

Winter	15.50	22.77	1999	5.21	1977	3.77	2007/12/03	53	35	10	2	9.4	67.5	1969
Spring	8.00	14.34	1997	3.24	1979	2.70	1972/03/05	42	23	3	0	1.4	18.2	1951
Summer	3.29	8.43	1968	0.84	1987	1.75	1968/06/01	20	9	2	0	-	-	-
Fall	11.40	18.61	2006	2.72	1952	5.02	2003/10/20	40	26	7	2	0.9	17.5	1985

Winter = Dec, Jan, and Feb		Spring = Mar, Apr, and May
Summer = Jun, Jul, and Aug.		Fall = Sep, Oct, and Nov