2001 SEATTLE, WASHINGTON SEATTLE – TACOMA AIRPORT (SEA)



The Seattle–Tacoma International Airport is located 6 miles south of the Seattle city limits and 14 miles north of Tacoma. It is situated on a low ridge lying between Puget Sound on the west and the Green River valley on the east with terrain sloping moderately to the shores of Puget Sound some 2 miles to the west. The Olympic Mountains, rising sharply from Puget Sound, are about 50 miles to the northwest. Rather steep bluffs border the Green River Valley about 2.5 miles to the east and the foothills of the Cascade Range begin 10 to 15 miles to the east of the airport.

The mild climate of the Pacific Coast is modified by the Cascade Mountains and, to a lesser extent, by the Olympic Mountains. The 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 extremes of temperature that occur in western Washington are the result of the occasional pressure distributions that force the continental air into the Puget Sound area. But the prevailing southwesterly circulation keeps the average winter daytime temperatures in the 40s and the nighttime readings in the 30s. During the summer, daytime temperatures are usually in the 70s with nighttime lows in the 50s. Extremes of temperatures, both in the winter and summer, are usually of short duration. 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, however, 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. These disturbances are most vigorous during the winter as they move through western Washington. The storm track shifts to the north during the summer and those that reach the State are not the wind and rain producers of the winter months. Local summer afternoon showers and a few thunderstorms occur in the Seattle–Tacoma area but they do not contribute materially to the precipitation.

The occurrence of snow in the Seattle–Tacoma area is extremely variable and usually melts before accumulating 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 over water trajectory.

The highest winds recorded in the Seattle–Tacoma area were associated with strong storms crossing the state from the southwest. Prevailing winds are from the southwest but occasional severe winter storms will produce strong northerly winds. Winds during the summer months are relatively light with occasional land–sea breeze effects creating afternoon northerly winds of 8 to 15 miles an hour. Fog or low clouds that form over the southern Puget Sound area in the late summer, fall, and early winter months, often dominate the weather conditions during the late night and early morning hours with visibilities occasionally lower for a few hours near sunrise. Most of the summer clouds form along the coast and move into the Seattle area from the southwest.

Based on the 1951–1980 period, the average first occurrence of 32 degrees Fahrenheit in the fall is November 11 and the average last occurrence in the spring is March 24.

NORMALS, MEANS, AND EXTREMES

SEATTLE, WA (SEA)

LATITUDE:    LONGITUDE:     ELEVATION (FT):    TIME ZONE:    WBAN: 24233

47 27′ 41″ N  122 18′ 49″ W  GRND: 447  BARO: 450  PACIFIC (UTC + 8)

2001 Seattle, Washington Seattle – Tacoma Airport (SEA)

ELEMENT POR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR
TEMPERATURE F NORMAL DAILY MAXIMUM 30 45.0 49.5 52.7 57.2 63.9 69.9 75.2 75.2 69.3 59.7 50.5 45.1 59.4
MEAN DAILY MAXIMUM 54 44.6 48.8 52.2 57.3 64.0 69.3 75.0 74.8 69.5 59.4 50.6 45.4 59.2
HIGHEST DAILY MAXIMUM 57 64 70 75 85 93 96 100 99 98 89 74 64 100
YEAR OF OCCURRENCE 1981 1968 1987 1976 1963 1995 1994 1981 1988 1987 1949 1993 JUL 1994
MEAN OF EXTREME MAXS. 54 55.2 59.7 64.4 73.1 81.1 84.8 89.1 88.1 84.3 73.1 61.0 55.5 72.4
NORMAL DAILY MINIMUM 30 35.2 37.4 38.5 41.2 46.3 51.9 55.2 55.7 51.9 45.8 40.1 35.8 44.6
MEAN DAILY MINIMUM 54 34.7 36.6 37.9 41.1 46.4 51.3 54.6 54.8 51.2 45.2 39.6 35.8 44.1
LOWEST DAILY MINIMUM 57 0 1 11 29 28 38 43 44 35 28 6 6 0
YEAR OF OCCURRENCE 1950 1950 1955 1975 1954 1952 1954 1955 1972 1949 1955 1968 JAN 1950
MEAN OF EXTREME MINS. 54 21.9 25.4 29.2 33.8 38.4 45.2 49.0 49.0 43.0 34.7 28.2 24.1 35.2
NORMAL DRY BULB 30 40.1 43.5 45.6 49.2 55.1 60.9 65.2 65.5 60.6 52.8 45.3 40.5 52.0
MEAN DRY BULB 54 39.6 42.8 45.0 49.2 55.3 60.3 64.9 64.7 60.4 52.3 45.1 40.6 51.7
MEAN WET BULB 18 39.1 39.8 42.7 45.9 50.4 54.1 57.8 58.2 55.2 49.1 42.9 38.3 47.8
MEAN DEW POINT 18 35.6 35.5 38.4 41.2 45.6 49.3 52.5 53.3 50.7 45.9 40.0 35.1 43.6
NORMAL NO. DAYS WITH:
MAXIMUM 90 30 0.0 0.0 0.0 0.0 0.2 0.3 1.1 1.2 0.3 0.0 0.0 0.0 3.1
MAXIMUM 32 30 1.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 1.3 2.9
MINIMUM 32 30 9.6 5.3 3.0 0.2 0.0 0.0 0.0 0.0 0.0 0.2 3.6 8.6 30.5
MINIMUM 0 30 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
H/C NORMAL HEATING DEG. DAYS 30 772 602 601 474 307 144 58 65 156 378 591 760 4908
NORMAL COOLING DEG. DAYS 30 0 0 0 0 0 21 64 81 24 0 0 0 190
RH NORMAL (PERCENT) 30 78 75 74 71 69 67 65 68 73 79 80 80 73
HOUR 04 LST 30 81 80 82 83 82 81 81 83 86 86 84 82 83
HOUR 10 LST 30 79 77 74 71 68 66 65 68 73 79 80 81 73
HOUR 16 LST 30 74 67 61 57 54 53 49 50 57 67 75 77 62
HOUR 22 LST 30 78 76 75 74 72 70 68 70 75 81 81 80 75
S PERCENT POSSIBLE SUNSHINE 30 28 40 50 52 56 56 64 65 62 43 28 23 47
W/O MEAN NO. DAYS WITH:
HEAVY FOG(VISBY 1/4 MI) 57 4.8 3.2 2.3 1.1 0.7 0.7 1.5 2.5 4.9 6.9 5.0 5.9 39.5
THUNDERSTORMS 57 0.2 0.3 0.6 1.0 0.9 0.7 0.7 0.8 0.7 0.4 0.8 0.3 7.4
CLOUDINESS MEAN:
SUNRISE-SUNSET (OKTAS) 52 6.7 6.5 6.3 6.2 5.7 5.6 4.2 4.5 4.8 5.9 6.6 6.7 5.8
MIDNIGHT-MIDNIGHT (OKTAS) 32 6.6 6.1 5.8 5.9 5.5 5.3 4.1 4.2 4.4 5.3 6.3 6.4 5.5
MEAN NO. DAYS WITH:
CLEAR 52 2.8 3.0 3.4 2.7 4.4 5.1 10.2 9.0 8.1 4.0 2.5 2.3 57.5
PARTLY CLOUDY 52 3.9 4.2 5.8 7.3 8.8 7.9 9.5 9.7 8.5 7.4 4.2 3.9 81.1
CLOUDY 52 24.3 21.1 21.9 20.0 17.7 16.9 10.5 11.9 13.0 19.5 23.3 24.9 225.0
PR MEAN STATION PRESSURE(IN) 29 29.55 29.52 29.50 29.55 29.55 29.56 29.57 29.54 29.55 29.57 29.53 29.58 29.55
MEAN SEA-LEVEL PRES. (IN) 18 30.04 30.02 30.01 30.04 30.02 30.03 30.05 30.03 30.03 30.06 30.02 30.08 30.04
WINDS MEAN SPEED (MPH) 51 9.6 9.6 9.5 9.4 8.9 8.6 8.2 7.9 8.1 8.4 9.2 9.6 8.9
PREVAIL. DIR (TENS OF DEGS) 35 19 19 19 21 21 21 22 21 01 19 19 18 19
MAXIMUM 2-MINUTE:
SPEED (MPH) 5 40 37 44 29 25 26 22 22 36 32 37 37 44
DIR. (TENS OF DEGS) 20 23 19 22 21 22 22 01 20 18 20 22 19
YEAR OF OCCURRENCE 2000 1999 1999 2001 2001 1999 2001 1997 1999 1997 1998 2000 MAR 1999
MAXIMUM 5-SECOND:
SPEED (MPH) 5 52 49 60 40 36 32 31 29 43 44 48 48 60
DIR. (TENS OF DEGS) 20 21 18 21 27 23 23 34 21 18 21 22 18
YEAR OF OCCURRENCE 2000 1999 1999 2001 1999 1999 1999 1998 1999 1997 1998 2000 MAR 1999
PRECIPITATION NORMAL (IN) 30 5.38 3.99 3.54 2.33 1.70 1.50 0.76 1.14 1.88 3.23 5.83 5.91 37.19
MAXIMUM MONTHLY (IN) 57 12.92 9.11 8.40 6.53 4.76 3.90 2.39 4.59 5.95 8.95 11.62 11.85 12.92
YEAR OF OCCURRENCE 1953 1961 1950 1991 1948 1946 1983 1975 1978 1947 1998 1979 JAN 1953
MINIMUM MONTHLY (IN) 57 0.58 0.35 0.57 0.33 0.12 0.13 T 0.01 T 0.31 0.74 1.37 T
YEAR OF OCCURRENCE 1985 1993 1965 1956 1992 1951 1960 1974 1991 1987 1976 1978 SEP 1991
MAXIMUM IN 24 HOURS (IN) 57 3.22 3.41 2.86 3.32 1.83 2.08 0.85 1.75 2.23 3.74 3.58 2.61 3.74
YEAR OF OCCURRENCE 1986 1951 1972 1991 1969 1985 1981 1968 1978 1981 1990 1979 OCT 1981
NORMAL NO. DAYS WITH:
PRECIPITATION 0.01 30 18.0 15.4 16.8 13.6 10.6 8.4 5.0 6.1 9.1 12.2 17.6 18.7 151.5
PRECIPITATION 1.00 30 0.8 0.4 0.2 0.1 0.1 0.2 0.0 0.1 0.2 0.4 1.2 1.1 4.8
SNOWFALL NORMAL (IN) 30 4.1 1.2 0.7 0.1 T 0.0 0.0 0.0 0.0 0.1 1.1 3.1 10.4
MAXIMUM MONTHLY (IN) 52 57.2 13.1 18.2 2.3 T 0.0 T 0.0 T 2.0 17.5 22.1 57.2
YEAR OF OCCURRENCE 1950 1949 1951 1972 1993 1980 1972 1971 1985 1968 JAN 1950
MAXIMUM IN 24 HOURS (IN) 52 21.4 9.8 7.4 2.3 T 0.0 T 0.0 T 2.0 9.4 13.0 21.4
YEAR OF OCCURRENCE 1950 1990 1989 1972 1993 1980 1972 1971 1946 1968 JAN 1950
MAXIMUM SNOW DEPTH (IN) 47 21 11 7 2 0 0 0 0 0 2 8 10 21
YEAR OF OCCURRENCE 1969 1969 1989 1972 1971 1985 1974 JAN 1969
NORMAL NO. DAYS WITH:
SNOWFALL 1.0 30 1.4 0.3 0.3 0.1 0.0 0.0 0.0 0.0 0.0 0.* 0.3 1.0 3.4

2001 Seattle, Washington Seattle – Tacoma Airport (SEA)

PRECIPITATION (inches) 2001 SEATTLE, WASHINGTON WA (SEA)
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANNUAL
1972 7.24 8.11 6.74 4.12 0.69 1.81 1.34 1.13 4.10 0.72 3.38 8.98 48.36
1973 4.29 1.89 1.62 1.35 1.60 2.50 0.08 0.27 1.81 3.31 7.99 8.33 35.04
1974 7.78 4.01 5.84 2.39 1.37 1.25 1.51 0.01 0.21 1.99 5.06 6.45 37.87
1975 6.01 5.80 2.87 2.49 1.13 0.84 0.27 4.59 T 7.75 5.07 7.66 44.48
1976 5.55 4.74 2.71 1.67 1.61 0.63 1.17 2.71 1.25 2.06 0.74 1.86 26.70
1977 1.77 1.58 3.80 0.55 3.70 0.54 0.42 3.59 2.55 2.60 5.27 6.47 32.84
1978 4.30 3.59 2.43 4.19 1.79 0.75 1.40 1.19 5.95 0.98 6.05 1.37 33.99
1979 2.25 5.32 1.55 0.81 0.88 0.46 0.73 1.02 2.07 3.38 1.94 11.85 32.26
1980 4.09 5.04 2.10 3.23 0.97 1.77 0.46 0.64 1.43 1.32 7.16 7.39 35.60
1981 2.42 4.45 2.23 1.58 1.33 2.31 1.38 0.25 3.42 6.40 4.07 5.56 35.40
1982 5.35 7.57 3.73 2.07 0.63 1.03 0.59 0.62 1.49 4.07 5.31 6.86 39.32
1983 7.07 4.57 3.81 1.06 2.10 1.85 2.39 1.90 1.85 1.34 7.97 5.02 40.93
1984 3.62 3.91 3.91 2.87 3.38 2.81 0.17 0.13 1.01 2.14 8.09 4.95 36.99
1985 0.58 2.63 2.56 1.30 0.85 2.80 0.10 0.55 1.98 5.74 4.26 1.78 25.13
1986 8.54 4.41 2.67 1.38 1.71 0.68 1.10 0.10 1.89 4.21 7.98 3.67 38.34
1987 5.98 2.05 5.53 2.61 2.38 0.16 0.39 0.29 0.91 0.31 3.21 6.11 29.93
1988 4.07 0.71 3.75 3.20 3.01 1.56 0.50 0.28 1.75 2.24 8.43 3.48 32.98
1989 2.78 3.43 5.79 2.80 2.78 1.14 0.64 0.89 0.54 2.98 6.13 4.79 34.69
1990 9.41 3.72 2.58 2.54 1.98 3.05 0.58 0.71 0.05 5.79 10.71 3.63 44.75
1991 4.46 4.69 4.66 6.53 1.39 1.29 0.28 2.17 T 1.31 5.33 3.31 35.42
1992 7.82 3.09 1.68 4.12 0.12 1.14 0.89 0.66 1.15 2.45 5.57 4.09 32.78
1993 4.09 0.35 4.80 4.54 2.86 2.48 1.27 0.16 0.03 1.54 2.20 4.48 28.80
1994 2.51 4.47 3.17 2.27 1.43 1.25 0.28 0.30 1.69 3.51 5.79 8.15 34.82
1995 4.48 4.97 4.07 2.05 0.81 1.46 1.34 1.81 0.91 3.93 10.40 6.37 42.60
1996 7.34 8.35 2.06 5.37 2.07 0.59 0.77 1.32 1.85 5.54 5.23 10.18 50.67
1997 7.02 1.99 8.15 4.32 1.87 1.64 1.20 1.27 3.41 5.83 3.93 2.63 43.26
1998 7.15 3.31 3.96 0.99 1.98 1.11 0.41 0.35 0.72 3.48 11.62 8.98 44.06
1999 6.84 6.95 3.66 1.49 2.12 1.86 1.18 0.92 0.17 2.26 9.60 5.06 42.11
2000 3.77 5.25 2.82 1.48 3.27 1.61 0.23 0.33 1.12 3.00 3.27 2.51 28.66
2001 2.70 2.07 2.73 3.16 1.39 3.05 1.03 2.32 0.83 3.13 9.26 5.89 37.56
POR=58 YRS 5.58 4.27 3.73 2.57 1.72 1.53 0.72 1.02 1.76 3.56 5.96 5.83 38.25

2001 Seattle, Washington Seattle – Tacoma Airport (SEA)

AVERAGE TEMPERATURE (F) 2001 SEATTLE, WASHINGTON WA (SEA)
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANNUAL
1972 37.0 41.4 46.9 47.0 58.3 60.1 66.0 66.7 55.4 50.1 46.7 38.1 51.1
1973 38.7 43.9 44.1 48.6 56.5 59.3 64.7 61.6 61.9 52.2 43.7 44.4 51.6
1974 38.7 43.2 46.3 50.3 54.9 62.6 64.0 64.6 64.4 52.5 45.1 42.4 52.4
1975 38.8 40.8 42.9 45.8 54.6 60.7 67.5 63.2 63.0 51.4 44.9 41.5 51.3
1976 41.8 40.9 41.3 49.5 56.4 60.0 65.9 64.1 62.6 54.9 47.8 44.7 52.5
1977 39.4 48.7 45.7 53.6 54.5 63.0 65.1 68.5 58.9 52.2 43.9 42.2 53.0
1978 44.4 46.0 48.6 49.9 54.5 64.3 65.8 65.5 58.8 54.3 41.2 37.5 52.6
1979 37.8 42.3 49.3 50.8 57.2 62.5 67.4 64.0 62.6 54.2 43.9 44.1 53.0
1980 34.8 43.8 44.3 51.6 54.2 57.5 63.8 61.9 59.6 53.9 46.7 44.1 51.4
1981 44.4 44.2 48.8 49.6 54.7 57.5 63.3 68.1 61.1 50.9 47.2 41.7 52.6
1982 39.3 42.1 44.1 47.4 54.7 63.1 62.8 65.1 60.6 52.7 43.2 40.8 51.3
1983 45.0 46.9 49.4 50.7 57.7 59.9 63.3 65.6 58.3 51.7 47.8 36.1 52.7
1984 43.2 44.8 48.5 48.7 52.9 58.8 65.0 64.9 59.9 49.7 44.6 36.8 51.5
1985 37.1 39.0 43.3 49.2 54.8 60.0 68.6 65.2 58.1 51.4 35.8 36.2 49.9
1986 44.9 42.8 49.2 48.1 55.7 62.7 61.7 68.4 59.1 54.3 45.3 42.0 52.9
1987 40.5 46.3 48.9 52.0 56.9 62.6 64.2 66.1 62.6 55.8 48.5 39.2 53.6
1988 40.1 44.4 45.6 50.3 54.9 59.6 65.3 65.4 60.5 55.4 45.4 41.9 52.4
1989 40.5 35.9 43.7 53.4 56.0 63.2 64.5 65.3 64.1 53.1 47.0 42.9 52.5
1990 42.5 40.0 47.1 52.1 54.7 59.8 68.0 67.3 63.4 51.2 46.6 35.3 52.3
1991 40.0 47.7 44.1 49.1 54.3 58.9 66.8 66.6 62.9 52.9 47.3 43.7 52.9
1992 43.9 47.3 50.3 53.1 59.8 65.0 66.7 66.8 60.0 54.4 45.5 38.8 54.3
1993 37.9 42.3 48.1 50.6 59.6 60.6 61.2 65.5 61.9 55.4 42.0 41.4 52.2
1994 44.9 40.4 48.5 52.3 58.2 60.6 67.9 67.3 64.4 52.8 42.4 41.7 53.5
1995 46.4 45.9 47.8 51.8 60.1 62.7 67.0 63.0 64.0 52.5 49.1 42.4 54.4
1996 39.7 43.2 47.2 51.5 53.1 60.5 67.9 66.5 59.2 51.1 43.1 39.3 51.9
1997 41.1 41.9 44.8 49.2 58.2 59.5 64.5 67.7 62.2 51.3 48.4 41.5 52.5
1998 42.2 45.8 46.6 50.4 54.9 59.9 67.6 66.8 63.1 52.6 46.7 39.9 53.0
1999 42.0 42.5 44.3 48.5 51.8 58.2 62.4 64.8 60.8 52.2 47.9 42.0 51.5
2000 40.3 43.7 44.5 50.9 53.8 60.6 64.3 63.5 60.2 52.8 42.5 40.8 51.5
2001 42.0 40.7 45.4 48.0 55.4 57.6 62.5 64.8 59.8 50.9 46.7 41.5 51.3
POR=57 YRS 39.6 42.8 44.9 49.1 55.3 60.3 64.9 64.6 60.2 52.3 45.0 40.5 51.6

REFERENCE NOTES:

PAGE 1:

THE TEMPERATURE GRAPH SHOWS NORMAL MAXIMUM AND NORMAL MINIMUM DAILY TEMPERATURES (SOLID CURVES) AND THE ACTUAL DAILY HIGH AND LOW TEMPERATURES (VERTICAL BARS).

PAGE 2 AND 3:

H/C INDICATES HEATING AND COOLING DEGREE DAYS.

RH INDICATES RELATIVE HUMIDITY

W/O INDICATES WEATHER AND OBSTRUCTIONS

S INDICATES SUNSHINE.

PR INDICATES PRESSURE.

CLOUDINESS ON PAGE 3 IS THE SUM OF THE CEILOMETER AND SATELLITE DATA NOT TO EXCEED EIGHT EIGHTHS (OKTAS).

GENERAL:

T INDICATES TRACE PRECIPITATION, AN AMOUNT GREATER THAN ZERO BUT LESS THAN THE LOWEST REPORTABLE VALUE.

+ INDICATES THE VALUE ALSO OCCURS ON EARLIER DATES.

BLANK ENTRIES DENOTE MISSING OR UNREPORTED DATA.

NORMALS ARE 30–YEAR AVERAGES (1961–1990).

ASOS INDICATES AUTOMATED SURFACE OBSERVING SYSTEM.

PM INDICATES THE LAST DAY OF THE PREVIOUS MONTH.

POR (PERIOD OF RECORD) BEGINS WITH THE JANUARY DATA MONTH AND IS THE NUMBER OF YEARS USED TO COMPUTE THE MEAN. INDIVIDUAL MONTHS WITHIN THE POR MAY BE MISSING.

WHEN THE POR FOR A NORMAL IS LESS THAN 30 YEARS, THE NORMAL IS PROVISIONAL AND IS BASED ON THE NUMBER OF YEARS INDICATED.

0.* OR * INDICATES THE VALUE OR MEAN–DAYS–WITH IS BETWEEN 0.00 AND 0.05.

CLOUDINESS FOR ASOS STATIONS DIFFERS FROM THE NON–ASOS OBSERVATION TAKEN BY A HUMAN OBSERVER. ASOS STATION CLOUDINESS IS BASED ON TIME–AVERAGED CEILOMETER DATA FOR CLOUDS AT OR BELOW 12,000 FEET AND ON SATELLITE DATA FOR CLOUDS ABOVE 12,000 FEET.

THE NUMBER OF DAYS WITH CLEAR, PARTLY CLOUDY, AND CLOUDY CONDITIONS FOR ASOS STATIONS IS THE SUM OF THE CEILOMETER AND SATELLITE DATA FOR THE SUNRISE TO SUNSET PERIOD.

GENERAL CONTINUED:

CLEAR INDICATES 0–2 OKTAS, PARTLY CLOUDY INDICATES 3–6 OKTAS, AND CLOUDY INDICATES 7 OR 8 OKTAS. WHEN AT LEAST ONE OF THE ELEMENTS (CEILOMETER OR SATELLITE) IS MISSING, THE DAILY CLOUDINESS IS NOT COMPUTED.

WIND DIRECTION IS RECORDED IN TENS OF DEGREES (2 DIGITS) CLOCKWISE FROM TRUE NORTH. "00" INDICATES CALM. "36" INDICATES TRUE NORTH.

RESULTANT WIND IS THE VECTOR AVERAGE OF THE SPEED AND DIRECTION.

AVERAGE TEMPERATURE IS THE SUM OF THE MEAN DAILY MAXIMUM AND MINIMUM TEMPERATURE DIVIDED BY 2.

SNOWFALL DATA COMPRISE ALL FORMS OF FROZEN PRECIPITATION, INCLUDING HAIL.

A HEATING (COOLING) DEGREE DAY IS THE DIFFERENCE BETWEEN THE AVERAGE DAILY TEMPERATURE AND 65 F.

DRY BULB IS THE TEMPERATURE OF THE AMBIENT AIR.

DEW POINT IS THE TEMPERATURE TO WHICH THE AIR MUST BE COOLED TO ACHIEVE 100 PERCENT RELATIVE HUMIDITY.

WET BULB IS THE TEMPERATURE THE AIR WOULD HAVE IF THE MOISTURE CONTENT WAS INCREASED TO 100 PERCENT RELATIVE HUMIDITY.

ON JULY 1, 1996, THE NATIONAL WEATHER SERVICE BEGAN USING THE "METAR" OBSERVATION CODE THAT WAS ALREADY EMPLOYED BY MOST OTHER NATIONS OF THE WORLD. THE MOST NOTICEABLE DIFFERENCE IN THIS ANNUAL PUBLICATION WILL BE THE CHANGE IN UNITS FROM TENTHS TO EIGHTS (OKTAS) FOR REPORTING THE AMOUNT OF SKY COVER.

2001 Seattle, Washington Seattle – Tacoma Airport (SEA)

HEATING DEGREE DAYS (base 65 F) 2001 SEATTLE, WASHINGTON WA (SEA)
YEAR JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN TOTAL
1972-73 48 32 295 455 544 825 807 586 639 484 272 183 5170
1973-74 70 114 111 388 633 632 809 606 573 433 306 99 4774
1974-75 60 66 74 380 591 690 804 671 678 570 317 144 5045
1975-76 23 73 93 413 594 723 712 693 731 465 265 157 4942
1976-77 24 52 81 307 510 625 786 451 591 335 320 79 4161
1977-78 34 43 178 390 625 701 631 525 498 447 323 78 4473
1978-79 44 42 180 324 706 846 837 630 479 420 235 96 4839
1979-80 27 40 86 327 628 642 929 610 634 395 329 218 4865
1980-81 66 104 158 343 543 639 633 577 494 455 316 220 4548
1981-82 80 28 138 430 530 715 790 636 640 521 312 103 4923
1982-83 93 42 141 373 647 745 613 502 479 422 244 149 4450
1983-84 72 19 196 406 511 890 672 577 507 482 372 183 4887
1984-85 54 42 159 467 603 867 857 719 666 469 310 160 5373
1985-86 8 48 199 413 870 888 618 616 479 502 305 90 5036
1986-87 105 12 196 323 586 707 754 522 491 384 253 105 4438
1987-88 58 37 102 284 485 792 767 590 593 435 316 165 4624
1988-89 60 38 162 291 583 708 749 807 654 340 273 93 4758
1989-90 41 29 68 362 534 677 689 696 547 379 312 158 4492
1990-91 29 23 61 420 546 913 767 475 639 472 322 179 4846
1991-92 24 40 90 368 526 654 645 507 447 351 171 63 3886
1992-93 26 22 151 322 580 805 834 629 517 427 170 135 4618
1993-94 113 48 120 290 685 723 618 682 503 373 209 132 4496
1994-95 23 5 43 369 671 713 570 527 527 390 160 118 4116
1995-96 19 77 60 382 471 693 779 630 543 399 362 135 4550
1996-97 42 32 167 422 649 793 732 640 622 468 211 159 4937
1997-98 38 11 95 416 489 718 700 533 562 433 307 152 4454
1998-99 21 21 79 376 543 771 706 623 634 487 400 218 4879
1999-00 101 42 141 393 504 706 760 611 628 415 340 154 4795
2000-01 60 65 146 373 668 745 707 675 599 504 305 218 5065
2001- 86 44 150 430 547 723

2001 Seattle, Washington Seattle – Tacoma Airport (SEA)

COOLING DEGREE DAYS (base 65 F) 2001 SEATTLE, WASHINGTON WA (SEA)
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANNUAL
1972 0 0 0 0 22 3 85 91 11 0 0 0 212
1973 0 0 0 0 16 19 67 17 21 0 0 0 140
1974 0 0 0 0 0 36 38 62 60 0 0 0 196
1975 0 0 0 0 0 21 108 29 39 0 0 0 197
1976 0 0 0 8 4 14 59 29 15 0 0 0 129
1977 0 0 0 0 0 26 44 158 4 0 0 0 232
1978 0 0 0 0 4 66 76 64 0 0 0 0 210
1979 0 0 0 0 2 27 106 15 21 0 0 0 171
1980 0 0 0 0 0 0 34 15 3 2 0 0 54
1981 0 0 0 0 1 3 35 131 24 0 0 0 194
1982 0 0 0 0 0 53 31 55 15 0 0 0 154
1983 0 0 0 0 24 2 24 44 0 0 0 0 94
1984 0 0 0 0 1 5 62 45 11 0 0 0 124
1985 0 0 0 0 3 17 125 59 0 0 0 0 204
1986 0 0 0 0 22 27 10 124 26 0 0 0 209
1987 0 0 0 0 11 42 39 80 35 5 0 0 212
1988 0 0 0 0 7 10 79 56 36 1 0 0 189
1989 0 0 0 0 2 47 32 45 46 0 0 0 172
1990 0 0 0 0 0 10 129 100 21 0 0 0 260
1991 0 0 0 0 0 0 85 96 34 0 0 0 215
1992 0 0 0 0 18 68 83 85 8 0 0 0 262
1993 0 0 0 0 10 8 1 72 32 0 0 0 123
1994 0 0 0 0 1 5 120 86 29 0 0 0 241
1995 0 0 0 0 15 55 88 20 34 0 0 0 212
1996 0 0 0 1 0 2 137 81 1 0 0 0 222
1997 0 0 0 0 4 0 29 100 17 0 0 0 150
1998 0 0 0 2 1 6 108 84 29 0 0 0 230
1999 0 0 0 0 0 18 29 43 22 0 0 0 112
2000 0 0 0 0 0 28 44 27 8 0 0 0 107
2001 0 0 0 0 11 3 14 44 0 0 0 0 72

2001 Seattle, Washington Seattle – Tacoma Airport (SEA)

SNOWFALL (inches) 2001 SEATTLE, WASHINGTON WA (SEA)
YEAR JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN TOTAL
1972-73 0.0 0.0 T 0.0 T 5.6 2.7 T 0.8 T 0.0 0.0 9.1
1973-74 0.0 0.0 0.0 0.0 0.2 0.3 3.7 T T 0.0 T 0.0 4.2
1974-75 0.0 0.0 0.0 0.0 0.0 9.8 1.3 T T 0.2 0.0 0.0 11.3
1975-76 0.0 0.0 0.0 0.0 1.6 2.6 T 0.5 0.2 T 0.0 0.0 4.9
1976-77 0.0 0.0 0.0 0.0 0.0 T 1.0 T 0.9 0.0 0.0 0.0 1.9
1977-78 0.0 0.0 0.0 0.0 3.5 T T 0.0 T T 0.0 0.0 3.5
1978-79 0.0 0.0 0.0 0.0 4.9 0.2 0.5 0.4 0.0 0.0 0.0 0.0 6.0
1979-80 0.0 0.0 0.0 0.0 0.0 1.2 8.8 2.5 0.1 T 0.0 0.0 12.6
1980-81 T 0.0 0.0 0.0 T 0.3 0.0 1.1 0.0 0.0 0.0 0.0 1.4
1981-82 0.0 0.0 0.0 0.0 0.0 T 7.0 T 2.0 T 0.0 0.0 9.0
1982-83 0.0 0.0 0.0 T 0.0 T 0.0 0.0 0.0 0.0 0.0 0.0 T
1983-84 0.0 0.0 0.0 0.0 T 0.3 T 0.0 0.0 T 0.0 0.0 0.3
1984-85 0.0 0.0 0.0 T T 2.4 T 5.7 T T 0.0 0.0 8.1
1985-86 0.0 0.0 0.0 T 17.5 1.7 0.0 1.1 0.0 T 0.0 0.0 20.3
1986-87 0.0 0.0 0.0 0.0 T 0.0 1.4 0.0 0.0 0.0 0.0 0.0 1.4
1987-88 0.0 0.0 0.0 0.0 0.0 T T 0.0 T 0.0 0.0 0.0 T
1988-89 0.0 0.0 0.0 0.0 T T 1.0 5.8 7.4 T T 0.0 14.2
1989-90 0.0 0.0 0.0 0.0 0.0 0.0 T 9.8 T 0.0 T 0.0 9.8
1990-91 0.0 0.0 0.0 0.0 0.0 3.8 0.4 0.0 2.5 T 0.0 0.0 6.7
1991-92 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
1992-93 0.0 0.0 0.0 0.0 T 6.7 1.3 1.4 0.0 0.0 T 0.0 9.4
1993-94 0.0 0.0 0.0 0.0 T 0.0 0.0 2.1 0.2 0.0 0.0 0.0 2.3
1994-95 0.0 0.0 0.0 0.0 T 1.9 0.0 0.2 T 0.0 0.0 0.0 2.1
1995-96 0.0 0.0 0.0 0.0 0.0 0.0 10.5 0.5 0.0 0.0 0.0 0.0 11.0
1996-97 0.0 0.0 0.0
1997-98
1998-99
1999-00
2000-01
2001-
POR=51 YRS T 0.0 T 0.0 1.1 2.4 4.8 1.6 1.3 0.1 T 0.0 11.3



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