STATION:  NAPA COUNTY AIRPORT (KAPC), CA

CLIMATOLOGICAL SUMMARY.  Period of Record: May 1998 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
                    |                                                                         |
Avg Max Temp        |  55.4  59.7  64.4  66.7  73.2  78.1  78.9  79.7  79.4  74.0  63.9  56.5 |   69.1
Avg Min Temp        |  36.8  38.3  39.8  41.1  46.1  50.4  53.4  52.6  49.4  43.8  39.7  36.3 |   44.0
Avg Temperature     |  46.1  49.0  52.1  53.9  59.7  64.2  66.1  66.2  64.4  58.9  51.8  46.4 |   56.6
                    |                                                                         |
Extremes:           |                                                                         |
    Extreme Max Temp|    68    77    85    91   101   110   106   101   102    95    84    78 |    110
                    |                                                                         |
    Date of Ext-Day |    21    16    10    26    15    14    22    03    21    12    15    19 |
               -Year|  2007  2007  2004  2004  2008  2000  2006  1998  2003  2001  2005  1999 |
                    |                                                                         |
    Extreme Min Temp|    18    23    28    25    33    36    43    42    37    30    22    19 |     18
                    |                                                                         |
    Date of Ext-Day |    15    08    08    24    09    08    01    31    25    31    12    22 |
               -Year|  2007  2003  2002  2008  2003  1999  2007  2008  2005  2002  2000  1998 |
                    |                                                                         |
Heating Degree Days |   586   452   401   334   181    69    30    26    69   195   397   575 |   3315
Cooling Degree Days |     0     0     1     1    16    46    65    61    51     6     0     0 |    247
                    |                                                                         |
Avg Number of Days: |                                                                         |
    Max Temp >= 90  |   0.0   0.0   0.0   0.2   1.4   3.1   2.5   2.9   4.8   0.7   0.0   0.0 |   15.5
    Max Temp >= 75  |   0.0   0.2   3.2   4.4  11.0  18.5  22.0  23.2  19.8  13.4   2.2   0.1 |  118.0
    Max Temp <= 32  |   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
                    |                                                                         |
    Min Temp <= 32  |   9.6   5.1   2.4   1.9   0.0   0.0   0.0   0.0   0.0   0.1   4.7  11.5 |   35.2
    Min Temp <= 20  |   0.2   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.3 |    0.5
    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
                    |                                                                         |
Avg Dew Point Temp  |  40.7  42.5  44.1  44.8  48.8  51.3  54.4  54.3  50.8  45.2  44.2  40.4 |   46.8
Avg Wet Bulb Temp   |  43.7  46.0  48.1  49.3  53.5  56.6  58.6  58.5  56.1  50.9  48.1  43.6 |   51.1
                    |                                                                         |
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                    |                                                                         |
Avg Sea Level Pres  | 30.13 30.06 30.04 30.00 29.95 29.90 29.91 29.90 29.88 29.97 30.08 30.13 |  30.00
(Inches of Mercury) |                                                                         |
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                    |                                                                         |
WEATHER             |   Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec |   Year
See disclaimer below|                                                                         |
                    |                                                                         |
Avg Number of Days: |                                                                         |
    Thunderstorms   |   0.4   0.5   0.4   0.2   0.4   1.0   0.5   0.3   0.5   0.7   0.5   0.4 |    5.7
    Heavy Fog       |   7.4   4.0   4.3   2.1   1.6   0.6   0.5   1.5   2.6   4.0   6.5   5.5 |   40.5
    Fog             |  22.2  18.2  18.1  12.6  12.0   6.9   9.8  11.5  13.1  14.7  19.7  19.1 |  177.9
    Hail            |   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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                    |                                                                         |
PRECIPITATION (In)  |   Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec |   Year
                    |                                                                         |
Average Monthly     |  3.27  4.02  1.86  1.12  0.71  0.08  0.00  0.03  0.06  0.72  2.18  4.39 |  18.43
                    |                                                                         |
Maximum Daily       |  2.10  2.13  1.17  1.04  0.81  0.37  0.01  0.30  0.30  0.91  1.90  2.44 |   2.44
                    |                                                                         |
    Date of Ext-Day |    04    27    05    11    08    08    20    21    24    26    01    13 |
               -Year|  2008  2006  2006  1999  2005  2005  2005  2003  2001  2004  2008  2002 |
                    |                                                                         |
Avg Number of Days: |                                                                         |
    >= 0.01         |  12.6  12.3  10.3   6.8   4.1   0.9   0.3   0.5   2.0   4.5  11.1  12.5 |   77.9
    >= 0.10         |   7.3   7.6   5.0   3.6   1.7   0.2   0.0   0.1   0.1   1.9   4.1   7.5 |   39.1
    >= 0.25         |   4.3   4.8   2.6   1.5   1.3   0.1   0.0   0.1   0.1   0.9   2.8   5.0 |   23.5
    >= 0.50         |   2.1   2.6   1.0   0.4   0.6   0.0   0.0   0.0   0.0   0.5   1.5   2.8 |   11.6
    >= 1.00         |   0.5   1.1   0.1   0.1   0.0   0.0   0.0   0.0   0.0   0.0   0.5   1.3 |    3.5
                    |                                                                         |
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                    |                                                                         |
WIND (MPH)          |   Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec |   Year
                    |                                                                         |
Daily Avg Wind Speed|   6.8   6.5   7.1   8.5   9.1   9.9   9.9   9.1   7.4   6.0   5.5   6.6 |    7.7
Daily Avg Max 2-Min |  16.9  16.9  18.2  20.5  19.9  20.2  19.2  18.5  17.0  15.9  15.2  16.9 |   17.9
Daily Avg Peak Gust |  20.1  20.0  21.4  24.4  23.5  23.4  22.3  21.6  19.8  18.7  18.2  20.4 |   21.2
                    |                                                                         |
Maximum Daily Avg   |  18.2  19.2  18.0  17.3  20.2  17.9  15.9  15.5  14.3  20.4  16.4  18.0 |   20.4
                    |                                                                         |
Maximum 2-Minute Avg|    39    41    41    38    32    38    29    32    31    34    41    37 |     41
                    |                                                                         |
Date of Max 2min-Day|    04    28    01    08    02    05    26    12    17    21    24    16 |
               -Year|  2008  2002  2002  2005  2001  2007  2000  2008  2004  2000  2001  2002 |
                    |                                                                         |
Maximum Peak Gust   |    52    49    48    46    39    44    33    61    38    43    59    51 |     61
                    |                                                                         |
Date of Max Gust-Day|    04    28    01    08    02    05    26    12    22    21    08    16 |
               -Year|  2008  2002  2002  2005  2001  2007  2000  2008  2006  2000  2008  2002 |
                    |                                                                         |
Avg Number of Days: |                                                                         |
   Peak Gust >=30   |   3.0   3.9   3.8   5.9   4.8   2.8   2.3   1.4   1.0   1.6   2.1   3.8 |   36.4
   Peak Gust >=40   |   0.3   0.6   0.1   0.7   0.0   0.1   0.0   0.1   0.0   0.2   0.3   0.5 |    2.8
   Peak Gust >=50   |   0.1   0.0   0.0   0.0   0.0   0.0   0.0   0.1   0.0   0.0   0.2   0.1 |    0.5
                    |                                                                         |
   Max 2-Minute >=30|   1.1   0.9   1.0   1.5   0.8   0.3   0.0   0.2   0.2   0.3   0.6   0.0 |    6.8
   Max 2-Minute >=40|   0.0   0.1   0.1   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.1   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.