STATION:  HELENA REGIONAL AIRPORT (KHLN), 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        |  33.0  38.4  47.8  56.8  67.0  74.4  87.7  85.1  73.0  58.4  43.3  33.5 |   58.2
Avg Min Temp        |  13.5  18.4  24.8  31.7  41.2  48.8  55.5  52.5  43.6  33.3  22.9  14.9 |   33.4
Avg Temperature     |  23.3  28.4  36.3  44.2  54.1  61.6  71.6  68.8  58.3  45.9  33.1  24.2 |   45.8
                    |                                                                         |
Extremes:           |                                                                         |
    Extreme Max Temp|    61    65    78    93    93    99   105   102    97    87    75    60 |    105
                    |                                                                         |
    Date of Ext-Day |    07    27    30    18    24    28    12    03    02    01    12    01 |
               -Year|  2002  2006  2004  2001  2001  2007  2002  2001  2007  1997  1999  2008 |
                    |                                                                         |
    Extreme Min Temp|   -33   -15   -12     3    23    30    39    38    19     4   -14   -27 |    -33
                    |                                                                         |
    Date of Ext-Day |    12    17    08    02    08    10    16    19    23    31    28    26 |
               -Year|  1997  2006  2002  2002  1997  1999  1999  1996  2000  1996  2006  1996 |
                    |                                                                         |
Heating Degree Days |  1294  1033   891   623   350   149    15    30   229   593   956  1265 |   7428
Cooling Degree Days |     0     0     0     0    11    47   221   148    27     0     0     0 |    453
                    |                                                                         |
Avg Number of Days: |                                                                         |
    Max Temp >= 90  |   0.0   0.0   0.0   0.1   0.7   2.3  14.1  10.6   1.9   0.0   0.0   0.0 |   29.7
    Max Temp >= 75  |   0.0   0.0   0.1   1.7   8.4  14.8  29.2  27.5  14.5   2.1   0.2   0.0 |   98.4
    Max Temp <= 32  |  12.4   7.0   2.9   0.7   0.0   0.0   0.0   0.0   0.0   0.5   5.7  12.6 |   41.9
                    |                                                                         |
    Min Temp <= 32  |  29.6  26.6  25.4  14.9   3.8   0.2   0.0   0.0   1.9  12.5  24.7  29.5 |  168.9
    Min Temp <= 20  |  19.2  15.0   8.0   2.8   0.0   0.0   0.0   0.0   0.1   1.9  10.8  20.2 |   77.9
    Min Temp  <= 0  |   5.5   1.9   0.9   0.0   0.0   0.0   0.0   0.0   0.0   0.0   0.8   4.0 |   13.2
                    |                                                                         |
Avg Dew Point Temp  |  13.9  17.1  20.6  26.6  34.5  42.4  44.6  43.0  37.2  29.8  21.3  14.6 |   28.8
Avg Wet Bulb Temp   |  20.3  24.3  30.0  36.5  44.6  51.2  56.5  54.4  47.3  38.5  28.5  21.1 |   37.8
                    |                                                                         |
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                    |                                                                         |
Avg Sea Level Pres  | 30.19 30.17 30.10 30.05 30.00 29.97 29.97 29.99 30.03 30.11 30.18 30.23 |  30.08
(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   |   0.0   0.0   0.1   0.4   2.8   5.5   5.7   5.2   1.2   0.2   0.0   0.1 |   21.1
    Heavy Fog       |   3.4   1.4   1.2   0.8   0.5   0.3   0.2   0.2   0.2   0.5   1.3   3.3 |   13.3
    Fog             |  13.4  10.2   7.4   5.7   5.2   5.2   1.6   2.8   3.1   5.5   8.8  11.3 |   80.2
    Hail            |   0.0   0.0   0.0   0.0   0.1   0.0   0.2   0.2   0.0   0.0   0.0   0.1 |    0.5
                    |                                                                         |
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                    |                                                                         |
PRECIPITATION (In)  |   Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec |   Year
                    |                                                                         |
Average Monthly     |  0.28  0.49  0.38  1.16  1.97  2.38  0.96  0.97  0.93  0.72  0.49  0.30 |  11.02
                    |                                                                         |
Maximum Daily       |  0.29  0.99  0.39  0.94  1.32  1.46  1.23  1.06  0.79  0.75  0.40  0.25 |   1.46
                    |                                                                         |
    Date of Ext-Day |    19    27    12    06    21    01    28    02    19    05    19    01 |
               -Year|  1998  2006  2005  2006  2007  2005  1998  2004  2004  2007  2007  2005 |
                    |                                                                         |
Avg Number of Days: |                                                                         |
    >= 0.01         |   6.1   7.0   6.4   8.7  10.8  12.8   6.7   7.1   5.7   6.5   6.3   5.9 |   89.9
    >= 0.10         |   0.8   1.1   1.2   3.4   5.0   6.2   3.0   3.3   2.5   2.2   1.8   1.3 |   31.9
    >= 0.25         |   0.1   0.3   0.3   1.3   2.8   2.9   1.2   1.1   1.4   0.7   0.5   0.1 |   12.7
    >= 0.50         |   0.0   0.2   0.0   0.5   1.0   1.3   0.3   0.2   0.4   0.2   0.0   0.0 |    4.1
    >= 1.00         |   0.0   0.0   0.0   0.0   0.2   0.3   0.1   0.1   0.0   0.0   0.0   0.0 |    0.7
                    |                                                                         |
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                    |                                                                         |
WIND (MPH)          |   Jan   Feb   Mar   Apr   May   Jun   Jul   Aug   Sep   Oct   Nov   Dec |   Year
                    |                                                                         |
Daily Avg Wind Speed|   5.9   6.3   7.8   8.1   8.1   7.9   7.0   6.4   6.4   6.4   5.8   6.0 |    6.8
Daily Avg Max 2-Min |  18.1  18.3  21.4  21.4  22.4  22.6  22.2  21.3  19.2  19.1  17.7  17.8 |   20.1
Daily Avg Peak Gust |  21.9  22.3  26.1  26.2  27.6  28.1  27.5  26.5  23.6  23.3  21.6  21.8 |   24.7
                    |                                                                         |
Maximum Daily Avg   |  18.8  23.0  21.1  20.8  19.3  18.9  16.1  15.8  20.5  21.2  21.7  21.3 |   23.0
                    |                                                                         |
Maximum 2-Minute Avg|    46    51    47    41    44    52    52    46    52    51    43    43 |     52
                    |                                                                         |
Date of Max 2min-Day|    30    02    28    20    26    24    14    24    25    31    18    27 |
               -Year|  1997  1999  2001  1997  1998  1999  2002  1999  1999  1999  2003  1997 |
                    |                                                                         |
Maximum Peak Gust   |    59    64    58    49    61    60    58    59    64    61    56    62 |     64
                    |                                                                         |
Date of Max Gust-Day|    30    02    06    20    20    24    13    24    25    31    17    31 |
               -Year|  2004  1999  2004  1997  2008  1999  2001  1999  1999  1999  2003  2008 |
                    |                                                                         |
Avg Number of Days: |                                                                         |
   Peak Gust >=30   |   8.7   7.1  10.9   9.2  12.0  12.6  12.1  10.8   7.6   8.2   7.6   9.1 |  115.9
   Peak Gust >=40   |   2.2   2.4   3.1   1.9   2.1   3.1   2.5   3.2   1.4   1.7   2.1   2.3 |   28.0
   Peak Gust >=50   |   0.5   0.6   0.3   0.0   0.4   0.7   0.3   0.4   0.3   0.3   0.4   0.5 |    4.7
                    |                                                                         |
   Max 2-Minute >=30|   3.1   3.3   5.2   3.2   4.3   4.0   4.0   4.2   2.6   3.0   3.4   0.0 |   40.3
   Max 2-Minute >=40|   0.5   0.5   0.5   0.1   0.3   0.7   0.5   0.4   0.4   0.3   0.4   0.0 |    4.6
                    |                                                                         |
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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.