STATION: SEATTLE-TACOMA INTERNATIONAL AIRPORT (KSEA), WA
CLIMATOLOGICAL SUMMARY. Period of Record: Jul 1996 to Dec 2008
Summaries based on unedited daily ASOS data. Errors may be present.
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TEMPERATURE (F) | Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec | Year
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Avg Max Temp | 46.5 49.2 52.1 57.6 63.7 68.9 75.7 75.7 69.4 58.6 50.8 45.7 | 59.5
Avg Min Temp | 36.8 36.7 39.1 41.9 47.4 51.9 56.0 56.0 52.1 45.9 40.1 36.2 | 45.0
Avg Temperature | 41.6 43.0 45.6 49.7 55.5 60.4 65.8 65.9 60.7 52.2 45.4 40.9 | 52.2
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Extremes: | |
Extreme Max Temp| 62 62 78 81 90 94 98 92 89 79 65 62 | 98
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Date of Ext-Day | 19 07 29 16 17 13 11 13 02 09 01 24 |
-Year| 2005 1998 2004 1999 2008 2002 2007 2002 2006 1996 2008 2005 |
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Extreme Min Temp| 19 23 28 32 35 42 46 50 42 30 18 14 | 14
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Date of Ext-Day | 12 18 05 02 07 08 25 31 28 31 28 20 |
-Year| 2007 2006 1998 1997 2002 2002 2004 1999 1999 2003 2006 2008 |
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Heating Degree Days | 725 622 602 459 299 162 47 35 141 396 587 746 | 4822
Cooling Degree Days | 0 0 0 0 5 23 72 63 13 0 0 0 | 177
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Avg Number of Days: | |
Max Temp >= 90 | 0.0 0.0 0.0 0.0 0.1 0.5 1.2 0.4 0.0 0.0 0.0 0.0 | 2.2
Max Temp >= 75 | 0.0 0.0 0.1 0.7 2.7 6.3 16.7 16.6 7.3 0.2 0.0 0.0 | 50.5
Max Temp <= 32 | 0.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.9 | 1.6
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Min Temp <= 32 | 6.3 5.9 2.3 0.2 0.0 0.0 0.0 0.0 0.0 0.4 3.1 6.7 | 24.9
Min Temp <= 20 | 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.7 | 1.2
Min Temp <= 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 | 0.0
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Avg Dew Point Temp | 36.4 35.5 38.4 40.0 45.3 49.2 52.8 53.7 50.8 45.7 40.1 35.8 | 43.6
Avg Wet Bulb Temp | 39.5 39.7 42.2 44.9 50.0 54.0 58.0 58.5 55.0 48.7 43.0 38.8 | 47.7
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Avg Sea Level Pres | 30.12 30.15 30.10 30.06 30.06 30.05 30.06 30.04 30.03 30.10 30.12 30.16 | 30.09
(Inches of Mercury) | |
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WEATHER | Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec | Year
See disclaimer below| |
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Avg Number of Days: | |
Thunderstorms | 0.2 0.2 0.7 0.3 0.8 0.8 0.2 0.8 0.1 0.4 0.8 0.2 | 5.5
Heavy Fog | 2.8 2.5 0.9 0.4 0.2 0.2 0.4 0.9 2.6 4.4 2.9 4.3 | 22.6
Fog | 20.2 14.8 14.4 10.4 9.8 9.2 5.8 7.0 10.7 16.7 16.9 19.2 | 155.0
Hail | 0.1 0.3 0.6 0.1 0.1 0.0 0.0 0.0 0.0 0.2 0.5 0.0 | 1.8
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PRECIPITATION (In) | Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec | Year
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Average Monthly | 6.21 3.05 3.89 2.38 1.77 1.58 0.62 1.06 1.43 3.52 6.74 5.91 | 38.18
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Maximum Daily | 2.39 1.34 1.86 1.45 0.74 1.16 0.65 1.41 1.19 5.02 3.29 3.77 | 5.02
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Date of Ext-Day | 17 01 18 13 09 11 16 22 30 20 06 03 |
-Year| 2005 2000 1997 2002 2000 2001 2001 2001 2007 2003 2006 2007 |
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Avg Number of Days: | |
>= 0.01 | 19.7 15.0 17.9 14.2 12.2 10.4 5.1 5.5 9.1 15.2 18.4 18.5 | 161.1
>= 0.10 | 14.0 8.2 10.5 7.6 5.6 4.4 2.1 2.7 4.2 7.8 12.5 12.8 | 92.5
>= 0.25 | 8.4 4.7 5.2 3.0 1.8 2.0 1.1 1.3 1.9 4.9 8.7 7.4 | 50.4
>= 0.50 | 4.1 1.7 1.8 0.8 0.8 1.0 0.2 0.7 0.6 1.9 4.2 3.5 | 21.3
>= 1.00 | 0.8 0.2 0.3 0.2 0.0 0.2 0.0 0.2 0.1 0.2 1.5 1.2 | 4.7
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WIND (MPH) | Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec | Year
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Daily Avg Wind Speed| 8.4 8.1 8.3 7.3 7.1 7.0 6.5 6.2 6.2 6.8 7.5 8.4 | 7.3
Daily Avg Max 2-Min | 18.0 17.2 17.9 16.0 14.9 14.5 13.5 13.4 13.7 15.3 16.7 18.3 | 15.8
Daily Avg Peak Gust | 22.4 21.4 22.6 20.0 18.8 18.2 16.8 16.6 17.0 19.1 20.9 23.1 | 19.7
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Maximum Daily Avg | 17.8 21.4 21.0 16.3 15.2 14.8 12.7 13.3 14.9 17.7 18.6 20.0 | 21.4
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Maximum 2-Minute Avg| 40 39 44 31 30 36 22 24 36 39 37 52 | 52
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Date of Max 2min-Day| 16 07 03 14 18 09 07 29 24 18 24 15 |
-Year| 2000 2008 1999 2002 2005 2008 1999 2008 1999 2007 1998 2006 |
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Maximum Peak Gust | 52 53 60 44 40 46 31 29 43 53 48 69 | 69
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Date of Max Gust-Day| 16 07 03 14 18 09 07 09 24 18 24 15 |
-Year| 2000 2008 1999 2002 2005 2008 1999 2008 1999 2007 1998 2006 |
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Avg Number of Days: | |
Peak Gust >=30 | 6.5 4.6 5.4 2.2 1.2 1.0 0.1 0.0 0.7 3.0 4.8 7.5 | 37.0
Peak Gust >=40 | 1.2 0.8 1.0 0.3 0.1 0.1 0.0 0.0 0.1 0.4 0.8 1.9 | 6.7
Peak Gust >=50 | 0.1 0.1 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.2 | 0.8
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Max 2-Minute >=30| 1.5 1.1 1.0 0.1 0.2 0.1 0.0 0.0 0.1 0.6 1.0 0.0 | 5.6
Max 2-Minute >=40| 0.1 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 | 0.3
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Observations of WEATHER may me innacurate due to early ASOS inconsistancies. Average days
with Thunderstorms may be low due to early mis-detection.
Heavy Fog = Visibility less than or equal to 1/4 mile.
Fog = Visibility greater than 1/4 mile or less than 7 miles.
Peak Gust = Maximum 5-second average.
Snowfall data not observed at ASOS stations.
Copyright ©2009 Western Regional Climate Center - Desert Research Institute - Reno, Nevada.