STATION:  DILLON AIRPORT (KDLN), MT

CLIMATOLOGICAL SUMMARY.  Period of Record: Jun 1997 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        |  32.9  36.8  46.0  54.3  63.6  71.5  84.8  82.0  70.6  57.0  42.8  32.1 |   56.2
Avg Min Temp        |  14.2  16.2  22.6  28.9  37.0  43.3  50.2  47.6  40.3  30.7  21.2  13.1 |   30.4
Avg Temperature     |  23.5  26.5  34.3  41.6  50.3  57.4  67.5  64.8  55.4  43.8  32.0  22.6 |   43.3
                    |                                                                         |
Extremes:           |                                                                         |
    Extreme Max Temp|    56    57    71    80    89    95   102    97    92    82    71    56 |    102
                    |                                                                         |
    Date of Ext-Day |    31    22    23    28    28    28    12    07    04    01    07    11 |
               -Year|  2003  2002  2004  2007  2003  2007  2002  2001  1998  1997  2006  2004 |
                    |                                                                         |
    Extreme Min Temp|   -29   -20   -15     9    20    30    34    30    18    -6   -16   -27 |    -29
                    |                                                                         |
    Date of Ext-Day |    05    24    08    03    08    04    16    31    24    31    29    21 |
               -Year|  2004  2003  2002  2002  2002  1998  1999  2006  2000  2002  2006  1998 |
                    |                                                                         |
Heating Degree Days |  1285  1089   952   702   457   240    30    66   298   656   990  1315 |   8080
Cooling Degree Days |     0     0     0     0     2    12   108    60    10     0     0     0 |    192
                    |                                                                         |
Avg Number of Days: |                                                                         |
    Max Temp >= 90  |   0.0   0.0   0.0   0.0   0.0   0.7   7.7   4.0   0.3   0.0   0.0   0.0 |   12.7
    Max Temp >= 75  |   0.0   0.0   0.0   0.4   5.7  12.6  28.9  26.6  11.7   1.5   0.0   0.0 |   87.3
    Max Temp <= 32  |  12.6   8.2   2.6   0.3   0.1   0.0   0.0   0.0   0.0   0.8   5.5  14.4 |   44.4
                    |                                                                         |
    Min Temp <= 32  |  30.4  27.6  28.0  21.7   8.4   0.9   0.0   0.1   3.3  17.6  26.1  30.2 |  194.2
    Min Temp <= 20  |  21.4  18.6  10.2   3.0   0.2   0.0   0.0   0.0   0.1   2.6  11.9  23.3 |   91.4
    Min Temp  <= 0  |   3.3   1.3   0.5   0.0   0.0   0.0   0.0   0.0   0.0   0.1   1.8   3.8 |   10.7
                    |                                                                         |
Avg Dew Point Temp  |  14.1  15.0  19.2  24.7  32.2  40.6  44.1  41.0  34.6  26.9  19.9  13.8 |   27.2
Avg Wet Bulb Temp   |  20.4  22.3  28.4  34.3  41.7  48.4  54.1  51.4  44.7  36.0  27.3  19.9 |   35.7
                    |                                                                         |
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                    |                                                                         |
Avg Sea Level Pres  | 30.16 30.12 30.06 30.02 29.96 29.94 29.94 29.96 29.99 30.07 30.14 30.20 |  30.05
(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   |   0.1   0.0   0.1   0.8   3.6   5.2   6.5   4.0   0.8   0.2   0.0   0.0 |   21.4
    Heavy Fog       |   1.2   1.7   1.3   1.9   0.5   0.3   0.0   0.0   0.1   1.0   1.0   1.1 |   10.0
    Fog             |   7.5   8.2   6.8   8.8   5.9   5.2   1.9   2.7   2.4   4.8   5.6   6.1 |   65.8
    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     |  0.23  0.31  0.41  1.10  1.83  1.95  0.80  0.88  0.84  0.89  0.28  0.28 |   9.79
                    |                                                                         |
Maximum Daily       |  0.30  0.37  0.55  0.72  1.02  1.58  1.23  0.83  0.54  0.86  0.34  0.48 |   1.58
                    |                                                                         |
    Date of Ext-Day |    14    01    27    05    22    06    17    15    06    07    25    03 |
               -Year|  2000  2003  2007  2006  2008  2007  2007  1997  2001  2006  1997  1998 |
                    |                                                                         |
Avg Number of Days: |                                                                         |
    >= 0.01         |   4.7   4.9   6.5   9.9  11.2  11.0   6.7   7.2   5.9   6.2   4.6   4.7 |   83.5
    >= 0.10         |   0.7   0.8   1.3   3.0   5.1   4.8   2.7   2.6   2.9   2.8   0.7   0.8 |   28.3
    >= 0.25         |   0.1   0.2   0.1   1.4   2.7   3.0   1.1   1.3   1.1   1.2   0.4   0.2 |   12.8
    >= 0.50         |   0.0   0.0   0.1   0.4   0.9   1.1   0.1   0.3   0.2   0.4   0.0   0.0 |    3.4
    >= 1.00         |   0.0   0.0   0.0   0.0   0.1   0.2   0.1   0.0   0.0   0.0   0.0   0.0 |    0.4
                    |                                                                         |
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                    |                                                                         |
WIND (MPH)          |   Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec |   Year
                    |                                                                         |
Daily Avg Wind Speed|  10.3   9.7  10.1   9.5   9.0   8.1   7.5   7.6   8.3   8.7   9.2   9.3 |    8.9
Daily Avg Max 2-Min |  21.1  20.7  22.7  23.9  24.0  23.0  22.2  21.9  20.4  20.2  19.9  20.6 |   21.7
Daily Avg Peak Gust |  24.6  24.2  27.3  28.6  29.0  28.4  27.5  27.1  24.9  24.2  23.6  24.1 |   26.1
                    |                                                                         |
Maximum Daily Avg   |  22.7  18.3  23.1  23.5  22.8  20.1  15.5  15.6  20.2  26.2  24.2  20.6 |   26.2
                    |                                                                         |
Maximum 2-Minute Avg|    43    46    47    55    43    49    54    40    49    48    40    46 |     55
                    |                                                                         |
Date of Max 2min-Day|    28    07    25    04    26    16    02    02    29    02    19    15 |
               -Year|  2008  1999  2007  2000  1998  2005  2000  1999  2002  1998  2003  2000 |
                    |                                                                         |
Maximum Peak Gust   |    53    56    59    70    58    67    71    66    70    55    52    55 |     71
                    |                                                                         |
Date of Max Gust-Day|    28    07    25    04    12    21    02    09    29    20    19    15 |
               -Year|  2008  2008  2007  2000  2001  2008  2000  2007  2002  2008  2003  2000 |
                    |                                                                         |
Avg Number of Days: |                                                                         |
   Peak Gust >=30   |   8.3   7.7  12.0  13.3  15.1  11.6  11.5  11.4   8.6   8.6   7.2   7.9 |  123.3
   Peak Gust >=40   |   1.4   1.5   2.9   3.3   3.2   3.0   3.8   3.8   1.8   1.5   1.7   1.8 |   29.7
   Peak Gust >=50   |   0.1   0.5   0.2   0.6   0.2   0.7   1.3   0.6   0.3   0.4   0.1   0.2 |    5.0
                    |                                                                         |
   Max 2-Minute >=30|   3.2   3.5   5.8   6.1   6.8   5.1   5.7   5.6   3.4   2.8   3.0   0.0 |   51.1
   Max 2-Minute >=40|   0.2   0.5   0.6   0.9   0.2   0.6   0.9   0.3   0.4   0.3   0.2   0.0 |    5.0
                    |                                                                         |
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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.