STATION:  GREAT FALLS INTERNATIONAL AIRPORT (KGTF), MT

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
                    |                                                                         |
Avg Max Temp        |  35.4  39.1  45.5  54.8  65.2  72.2  86.1  83.4  70.9  57.7  43.8  35.9 |   57.5
Avg Min Temp        |  15.5  18.1  22.3  30.1  38.7  46.2  52.6  50.9  43.1  33.1  24.9  16.8 |   32.7
Avg Temperature     |  25.5  28.6  33.9  42.4  51.9  59.2  69.4  67.2  57.0  45.4  34.3  26.4 |   45.1
                    |                                                                         |
Extremes:           |                                                                         |
    Extreme Max Temp|    63    63    78    80    90    96   104   101    95    85    76    59 |    104
                    |                                                                         |
    Date of Ext-Day |    23    27    30    29    12    30    06    11    02    01    07    06 |
               -Year|  2005  2006  2004  1998  2001  2008  2007  1996  1998  2008  1999  2003 |
                    |                                                                         |
    Extreme Min Temp|   -31   -25   -22    -8    17    31    30    36    16    -9   -21   -27 |    -31
                    |                                                                         |
    Date of Ext-Day |    12    17    08    21    02    10    26    17    23    31    28    26 |
               -Year|  1997  2006  2002  2008  2005  1999  2003  2002  2000  2002  2006  1996 |
                    |                                                                         |
Heating Degree Days |  1225  1029   964   677   410   198    32    54   266   608   921  1197 |   7581
Cooling Degree Days |     0     0     0     0     5    25   168   121    25     0     0     0 |    345
                    |                                                                         |
Avg Number of Days: |                                                                         |
    Max Temp >= 90  |   0.0   0.0   0.0   0.0   0.2   1.2  11.5   8.9   1.4   0.0   0.0   0.0 |   23.1
    Max Temp >= 75  |   0.0   0.0   0.1   1.4   6.9  11.8  28.4  25.5  11.9   2.4   0.1   0.0 |   88.5
    Max Temp <= 32  |   9.6   7.4   5.0   1.4   0.1   0.0   0.0   0.0   0.1   1.2   6.2   9.4 |   40.4
                    |                                                                         |
    Min Temp <= 32  |  27.1  26.2  25.7  18.3   6.8   0.3   0.1   0.0   2.1  14.7  21.9  26.6 |  169.7
    Min Temp <= 20  |  16.2  14.0  11.1   3.0   0.2   0.0   0.0   0.0   0.1   2.6   8.7  16.8 |   72.8
    Min Temp  <= 0  |   6.1   2.8   2.2   0.4   0.0   0.0   0.0   0.0   0.0   0.2   1.8   4.5 |   18.0
                    |                                                                         |
Avg Dew Point Temp  |  14.2  16.3  19.6  26.6  34.4  43.3  44.2  41.9  37.2  28.8  20.5  14.6 |   28.5
Avg Wet Bulb Temp   |  21.9  24.3  28.5  35.6  43.8  50.8  55.7  53.7  46.9  38.0  29.0  22.6 |   37.6
                    |                                                                         |
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                    |                                                                         |
Avg Sea Level Pres  | 30.12 30.11 30.08 30.05 29.98 29.93 29.92 29.95 29.98 30.07 30.11 30.14 |  30.04
(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   |   0.3   0.3   0.0   0.3   1.2   3.9   4.2   4.0   1.5   0.2   0.1   0.7 |   16.8
    Heavy Fog       |   1.4   2.3   3.2   1.9   0.8   0.3   0.0   0.1   0.7   2.2   1.9   2.2 |   16.9
    Fog             |   9.2   9.7  10.6   9.3   6.4   7.7   2.2   4.2   5.2   6.7   7.4   8.5 |   87.1
    Hail            |   0.0   0.0   0.0   0.0   0.4   0.4   0.3   0.4   0.2   0.0   0.0   0.1 |    1.8
                    |                                                                         |
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                    |                                                                         |
PRECIPITATION (In)  |   Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec |   Year
                    |                                                                         |
Average Monthly     |  0.39  0.43  0.71  1.27  2.23  2.95  0.91  1.26  1.45  0.75  0.47  0.39 |  13.20
                    |                                                                         |
Maximum Daily       |  0.47  0.50  1.00  0.81  1.88  2.24  1.18  1.37  1.09  0.75  0.52  0.38 |   2.24
                    |                                                                         |
    Date of Ext-Day |    15    23    19    18    30    10    20    23    17    12    27    29 |
               -Year|  2006  2007  2006  2007  1998  2002  1997  2004  1996  2000  2005  1996 |
                    |                                                                         |
Avg Number of Days: |                                                                         |
    >= 0.01         |   5.8   6.5   7.4  10.0  10.7  13.0   5.9   7.4   7.6   6.3   5.4   5.3 |   91.3
    >= 0.10         |   1.2   1.4   2.2   3.8   5.0   6.6   2.6   3.7   3.6   2.4   1.4   1.5 |   35.5
    >= 0.25         |   0.2   0.3   0.8   1.8   2.8   3.3   1.0   1.5   2.2   0.8   0.6   0.4 |   15.6
    >= 0.50         |   0.0   0.1   0.1   0.5   1.2   1.6   0.3   0.6   0.9   0.2   0.1   0.0 |    5.6
    >= 1.00         |   0.0   0.0   0.1   0.0   0.4   0.4   0.2   0.1   0.1   0.0   0.0   0.0 |    1.2
                    |                                                                         |
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                    |                                                                         |
WIND (MPH)          |   Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec |   Year
                    |                                                                         |
Daily Avg Wind Speed|  13.7  12.1  12.0  10.9  10.8   9.8   9.1   9.0  10.1  11.7  13.2  13.9 |   11.4
Daily Avg Max 2-Min |  25.5  22.4  23.7  23.0  23.4  22.6  22.3  22.3  21.6  23.4  24.6  25.7 |   23.4
Daily Avg Peak Gust |  29.6  26.2  28.2  27.7  28.4  27.9  27.7  27.7  26.3  27.7  29.0  30.2 |   28.0
                    |                                                                         |
Maximum Daily Avg   |  30.2  31.1  29.8  26.3  26.3  21.5  19.1  22.4  25.6  26.5  29.7  27.9 |   31.1
                    |                                                                         |
Maximum 2-Minute Avg|    51    54    49    52    48    52    43    51    49    54    58    55 |     58
                    |                                                                         |
Date of Max 2min-Day|    12    11    07    13    29    04    28    16    09    31    19    16 |
               -Year|  2002  2002  2004  2002  1998  2006  2001  2002  1998  1999  2003  1999 |
                    |                                                                         |
Maximum Peak Gust   |    64    66    63    58    53    64    59    83    57    62    72    67 |     83
                    |                                                                         |
Date of Max Gust-Day|    16    11    18    13    29    04    14    08    09    31    19    16 |
               -Year|  2000  2002  2004  2002  1998  2006  2002  2003  1998  1999  2003  1999 |
                    |                                                                         |
Avg Number of Days: |                                                                         |
   Peak Gust >=30   |  15.2  11.2  13.3  12.2  13.3  12.1  11.2  11.8  10.0  13.1  14.1  16.5 |  154.2
   Peak Gust >=40   |   5.7   2.7   4.9   2.2   3.1   2.8   3.3   4.1   2.8   3.9   5.1   6.8 |   47.2
   Peak Gust >=50   |   1.6   0.5   1.0   0.6   0.4   0.5   0.5   0.5   0.1   0.4   0.9   1.1 |    8.0
                    |                                                                         |
   Max 2-Minute >=30|  10.4   6.0   8.5   5.6   5.8   4.7   5.2   6.2   5.1   7.6   9.5   0.0 |   74.7
   Max 2-Minute >=40|   2.8   0.8   1.8   0.6   0.6   0.6   0.5   0.5   0.5   1.2   1.5   0.0 |   11.2
                    |                                                                         |
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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.