2001 HELENA, MONTANA (HLN)



Helena is located on the south side of an intermountain valley bounded on the west and south by the main chain of the Continental Divide. The valley is approximately 25 miles in width from north to south and 35 miles long from east to west. The average height of the mountains above the valley floor is about 3,000 feet.

The climate of Helena may be described as modified continental. Several factors enter into modifying the continental climate characteristics. Some of these are invasion by Pacific Ocean air masses, drainage of cool air into the valley from the surrounding mountains, and the protecting mountain shield in all directions.

The mountains to the north and east sometimes deflect shallow masses of invading cold Arctic air to the east. Following periods of extreme cold, when the return circulation of maritime air has brought warming to most of the eastern part of the state, cold air may remain trapped in the valley for several days before being replaced by warmer air. During these periods of transition from cold–to–warm temperatures, inversions are often quite pronounced.

As may be expected in a northern latitude, cold waves may occur from November through February, with temperatures occasionally dropping to zero or lower.

Summertime temperatures are moderate, with maximum readings generally under 90 degrees and very seldom reaching 100 degrees. Like all mountain stations, there is usually a marked change in temperature from day to night. During the summer this tends to produce an agreeable combination of fairly warm days and cool nights.

Most of the precipitation falls from April through July from frequent showers or thunderstorms, but usually with some steady rains in June, the wettest month of the year. Like summer, fall and winter months are relatively dry. During the April to September growing season, precipitation varies considerably.

Thunderstorms are rather frequent from May through August. Snow can be expected from September through May, but amounts during the spring and fall are usually light, and snow on the ground ordinarily lasts only a day or two. During the winter months snow may remain on the ground for several weeks at a time. There is little drifting of snow in the valley, and blizzard conditions are very infrequent.

Severe ice, sleet, and hailstorms are very seldom observed. Since 1880, only a few hailstorms have caused extensive damage in the city of Helena.

In winter, hours of sunshine are more than would be expected at a mountain location.

Due to the sheltering influence of the mountains, Foehn (Chinook) winds are not as pronounced as might be expected for a location on the eastern slopes of the Rocky Mountains. Strong winds can occur at any time throughout the year, but generally do not last more than a few hours at a time.

Based on the 1951–1980 period, the average first occurrence of 32 degrees Fahrenheit in the fall is September 18 and the average last occurrence in the spring is May 18.

NORMALS, MEANS, AND EXTREMES

HELENA, MT (HLN)

LATITUDE:    LONGITUDE:     ELEVATION (FT):    TIME ZONE:    WBAN: 24144

46 36′ 20″ N  111 57′ 49″ W  GRND: 3864  BARO: 3867  MOUNTAIN (UTC + 7)

2001 Helena, Montana (HLN)

ELEMENT POR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR
TEMPERATURE F NORMAL DAILY MAXIMUM 30 29.6 36.9 44.8 56.1 65.4 75.8 85.0 83.2 69.8 58.5 42.4 31.3 56.6
MEAN DAILY MAXIMUM 50 29.9 36.7 44.8 55.8 65.8 74.1 83.5 82.6 71.0 58.5 42.1 32.4 56.4
HIGHEST DAILY MAXIMUM 61 72 69 77 86 93 100 102 105 99 87 75 64 105
YEAR OF OCCURRENCE 2000 1995 1978 1992 2001 1988 1981 1969 1967 2001 1999 1980 AUG 1969
MEAN OF EXTREME MAXS. 54 52.3 55.4 64.2 75.3 83.6 90.7 95.8 95.5 88.8 77.7 61.9 52.9 74.5
NORMAL DAILY MINIMUM 30 9.6 15.9 22.3 30.6 39.6 48.3 53.4 51.7 41.0 31.6 20.7 11.2 31.3
MEAN DAILY MINIMUM 50 9.5 15.6 22.2 30.0 39.9 47.4 52.6 50.7 41.3 31.5 20.5 12.5 31.1
LOWEST DAILY MINIMUM 61 -42 -42 -30 1 17 30 36 28 18 -8 -39 -38 -42
YEAR OF OCCURRENCE 1957 1996 1955 1954 1954 1999 1971 1992 1970 1991 1959 1964 FEB 1996
MEAN OF EXTREME MINS. 54 -18.6 -9.3 -.2 16.8 27.8 36.4 42.8 40.3 27.7 15.7 -1.0 -13.8 13.7
NORMAL DRY BULB 30 19.6 26.4 33.6 43.4 52.5 62.1 69.2 67.4 55.4 45.1 31.6 21.2 44.0
MEAN DRY BULB 54 19.0 25.8 33.0 43.2 52.6 60.6 68.0 66.6 56.0 45.1 31.4 22.0 43.6
MEAN WET BULB 49 16.7 22.5 27.3 35.6 43.6 50.2 54.5 53.4 46.0 37.5 27.5 19.5 36.2
MEAN DEW POINT 49 9.6 15.3 19.2 25.9 34.3 41.6 44.5 42.8 36.9 29.2 20.6 13.2 27.8
NORMAL NO. DAYS WITH:
MAXIMUM 90 30 0.0 0.0 0.0 0.0 0.2 2.4 7.6 6.6 1.1 0.0 0.0 0.0 17.9
MAXIMUM 32 30 14.4 7.9 4.1 0.5 0.0 0.0 0.0 0.0 0.0 0.5 5.3 14.8 47.5
MINIMUM 32 30 29.4 26.0 27.3 18.0 3.7 0.1 0.0 0.0 3.6 16.6 26.7 29.5 180.9
MINIMUM 0 30 8.9 4.5 1.7 0.0 0.0 0.0 0.0 0.0 0.0 0.1 1.6 6.2 23.0
H/C NORMAL HEATING DEG. DAYS 30 1407 1081 973 648 388 137 34 65 321 617 1002 1358 8031
NORMAL COOLING DEG. DAYS 30 0 0 0 0 0 50 164 139 33 0 0 0 386
RH NORMAL (PERCENT) 30 66 64 60 54 54 52 46 48 54 58 65 68 57
HOUR 05 LST 30 70 72 72 70 72 71 66 66 73 73 73 72 71
HOUR 11 LST 30 66 62 55 46 45 44 39 41 48 52 62 67 52
HOUR 17 LST 30 62 54 46 38 38 36 29 30 36 42 57 66 44
HOUR 23 LST 30 69 68 65 60 60 58 50 52 60 64 69 71 62
S PERCENT POSSIBLE SUNSHINE 55 47 56 61 59 61 64 78 75 68 60 44 42 60
W/O MEAN NO. DAYS WITH:
HEAVY FOG(VISBY 1/4 MI) 61 1.9 1.2 1.8 0.3 0.2 0.1 0.1 0.1 0.1 0.5 1.4 2.3 10.0
THUNDERSTORMS 61 0.1 0.1 0.1 1.0 4.1 7.4 8.6 7.5 1.8 0.3 0.1 0.0 31.1
CLOUDINESS MEAN:
SUNRISE-SUNSET (OKTAS) 1 9.6 8.8 4.8
MIDNIGHT-MIDNIGHT (OKTAS) 1 3.2 8.8 4.8
MEAN NO. DAYS WITH:
CLEAR 1 1.5 2.0 2.0 8.0 2.0 11.0 7.0 1.0 6.0
PARTLY CLOUDY 1 1.0 5.0 1.0 6.0 5.0 1.0 3.0 5.0 7.0 2.0
CLOUDY 1 3.0 3.0 12.0 23.0 6.0 4.0 7.0 3.0
PR MEAN STATION PRESSURE(IN) 29 26.02 26.00 25.94 25.97 25.96 25.99 26.04 26.05 26.07 26.06 26.02 26.02 26.01
MEAN SEA-LEVEL PRES. (IN) 50 30.17 30.12 30.03 29.98 29.95 29.93 29.96 29.96 30.03 30.09 30.12 30.15 30.04
WINDS MEAN SPEED (MPH) 38 9.0 9.4 10.7 11.0 11.2 12.0 12.0 11.7 10.5 9.8 9.9 9.6 10.6
PREVAIL. DIR (TENS OF DEGS) 21 27 27 27 27 27 27 27 27 27 27 27 27 27
MAXIMUM 2-MINUTE:
SPEED (MPH) 7 46 51 47 41 44 52 47 46 52 51 39 44 52
DIR. (TENS OF DEGS) 29 26 28 28 29 18 26 26 26 28 27 28 26
YEAR OF OCCURRENCE 1997 1999 2001 1997 1996 1999 2001 1999 1999 1999 1995 1995 SEP 1999
MAXIMUM 5-SECOND:
SPEED (MPH) 7 55 64 56 49 55 60 58 59 64 61 47 57 64
DIR. (TENS OF DEGS) 28 26 28 27 25 19 26 26 26 26 27 29 26
YEAR OF OCCURRENCE 2000 1999 2000 1997 2001 1999 2001 1999 1999 1999 1995 1995 SEP 1999
PRECIPITATION NORMAL (IN) 30 0.63 0.41 0.73 0.97 1.78 1.87 1.10 1.29 1.15 0.60 0.48 0.59 11.60
MAXIMUM MONTHLY (IN) 61 2.78 1.20 1.62 3.00 6.09 4.74 4.70 4.23 3.37 2.68 1.50 1.48 6.09
YEAR OF OCCURRENCE 1969 1986 1982 1975 1981 1944 1993 1974 1965 1975 1950 1977 MAY 1981
MINIMUM MONTHLY (IN) 61 T 0.02 0.02 0.10 0.29 0.08 0.08 0.02 0.08 0.02 0.04 0.01 T
YEAR OF OCCURRENCE 1987 1991 1959 1977 1979 1985 1973 1988 1972 1978 1969 1997 JAN 1987
MAXIMUM IN 24 HOURS (IN) 61 0.77 0.58 1.01 1.25 2.31 1.78 2.26 1.86 1.61 1.01 0.82 0.51 2.31
YEAR OF OCCURRENCE 1969 1953 1957 1951 1981 1979 1983 1974 1980 2000 1959 1982 MAY 1981
NORMAL NO. DAYS WITH:
PRECIPITATION 0.01 30 8.2 6.5 8.6 8.1 11.1 10.1 7.1 7.6 7.1 5.2 6.9 8.2 94.7
PRECIPITATION 1.00 30 0.0 0.0 0.0 0.0 0.2 0.2 0.1 0.1 0.1 0.0 0.0 0.0 0.7
SNOWFALL NORMAL (IN) 30 9.1 5.6 7.4 5.5 1.7 0.1 T 0.0 1.6 2.2 5.0 8.5 46.7
MAXIMUM MONTHLY (IN) 57 35.6 19.7 21.6 20.6 12.7 2.7 T 6.2 13.7 11.0 32.9 22.8 35.6
YEAR OF OCCURRENCE 1969 1959 1955 1967 1967 1969 1993 1992 1965 1969 1959 1967 JAN 1969
MAXIMUM IN 24 HOURS (IN) 57 11.5 11.7 8.7 12.9 12.5 2.7 T 6.2 13.3 7.4 21.5 10.7 21.5
YEAR OF OCCURRENCE 1969 1993 1955 1960 1967 1969 1993 1992 1957 1969 1959 1991 NOV 1959
MAXIMUM SNOW DEPTH (IN) 46 23 15 15 8 8 T 0 0 10 6 19 14 23
YEAR OF OCCURRENCE 1969 1975 1969 1986 1967 1969 1965 1969 1978 1985 JAN 1969
NORMAL NO. DAYS WITH:
SNOWFALL 1.0 30 3.0 1.8 2.3 1.5 0.4 0.* 0.0 0.0 0.5 0.7 1.5 2.3 14.0

2001 Helena, Montana (HLN)

PRECIPITATION (inches) 2001 HELENA, MT (HLN)
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANNUAL
1972 1.12 0.54 0.63 0.41 0.77 1.12 0.56 1.63 0.08 0.57 0.33 0.46 8.22
1973 0.22 0.13 0.05 0.66 1.08 0.73 0.08 0.56 0.43 0.66 1.03 0.63 6.26
1974 0.66 0.23 0.38 0.76 2.07 0.34 0.49 4.23 0.22 0.51 0.30 0.26 10.45
1975 1.26 0.72 0.88 3.00 1.95 2.83 3.89 2.47 0.47 2.68 0.48 0.31 20.94
1976 0.26 0.38 0.41 1.34 0.87 2.74 0.29 1.58 1.82 0.04 0.30 0.04 10.07
1977 0.65 0.13 1.11 0.10 1.82 1.37 1.37 0.72 1.93 0.17 0.48 1.48 11.33
1978 0.96 0.61 0.31 0.94 1.20 0.44 2.83 0.59 1.11 0.02 1.19 0.76 10.96
1979 0.77 0.72 1.34 2.26 0.29 2.75 0.32 0.79 0.12 0.38 0.06 0.59 10.39
1980 0.62 0.74 0.88 0.63 4.32 3.16 1.92 0.28 2.57 1.21 0.32 0.40 17.05
1981 0.15 0.10 1.10 0.75 6.09 1.15 1.78 0.10 0.90 0.82 0.54 0.33 13.81
1982 0.80 0.58 1.62 0.54 1.77 2.99 0.49 0.74 2.74 0.35 0.31 1.05 13.98
1983 0.24 0.07 0.36 0.29 1.79 2.20 3.48 2.67 1.56 0.35 0.26 0.76 14.03
1984 0.17 0.15 0.49 1.45 1.03 2.14 0.11 1.11 0.73 0.74 0.47 0.41 9.00
1985 0.16 0.38 0.32 0.46 0.75 0.08 0.10 2.64 2.11 0.76 0.84 0.35 8.95
1986 0.32 1.20 0.49 1.08 0.83 1.56 1.37 1.84 2.45 0.03 0.54 0.38 12.09
1987 T 0.03 1.19 0.76 1.90 1.50 2.88 0.38 0.80 0.05 0.12 0.42 10.03
1988 0.27 0.50 0.45 1.32 1.82 1.50 0.36 0.02 2.09 0.69 0.69 0.32 10.03
1989 1.42 0.82 1.35 0.72 1.00 1.43 1.55 1.61 1.31 0.54 0.26 0.48 12.49
1990 0.47 0.14 0.91 0.43 1.54 0.92 0.40 2.57 0.11 0.11 0.36 0.47 8.43
1991 0.27 0.02 0.90 0.75 1.71 3.27 0.72 0.70 1.26 0.65 0.88 0.79 11.92
1992 0.29 0.10 0.60 0.55 0.64 2.36 1.06 1.01 0.09 1.87 0.19 0.57 9.33
1993 0.80 1.03 0.56 1.63 1.71 3.14 4.70 2.79 1.25 0.71 0.36 0.13 18.81
1994 0.20 0.40 0.32 1.45 1.23 0.84 0.71 0.47 0.09 1.14 0.55 0.07 7.47
1995 0.20 0.08 0.49 1.15 3.09 2.93 1.51 0.33 1.59 0.10 0.62 0.28 12.37
1996 0.55 0.11 0.58 0.70 2.42 1.20 1.27 0.89 0.51 0.04 0.84 0.61 9.72
1997 0.28 0.10 0.10 0.20 2.35 2.43 1.25 1.79 0.31 1.62 0.13 0.01 10.57
1998 0.49 0.12 0.39 0.64 2.27 3.03 2.96 0.50 0.82 0.14 1.07 0.14 12.57
1999 0.38 0.26 0.02 1.05 2.19 2.15 0.41 1.92 0.54 0.39 0.13 0.10 9.54
2000 0.26 0.32 0.26 0.73 0.98 1.42 0.73 0.43 0.54 2.12 0.36 0.23 8.38
2001 0.27 0.17 0.44 1.39 1.23 2.11 1.94 0.43 1.38 0.54 0.13 0.28 10.31
POR=120 YRS 0.69 0.51 0.71 0.98 1.87 2.17 1.15 0.97 1.13 0.76 0.61 0.61 12.16

2001 Helena, Montana (HLN)

AVERAGE TEMPERATURE (F) 2001 HELENA, MT (HLN)
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANNUAL
1972 12.4 26.8 39.1 39.8 50.9 61.8 61.7 66.0 50.9 39.0 31.1 13.6 41.1
1973 17.7 22.8 36.0 40.3 52.9 61.2 68.9 66.8 54.4 45.8 24.5 28.2 43.3
1974 18.1 32.8 33.9 46.0 48.6 64.9 70.4 61.5 53.5 45.8 34.7 27.7 44.8
1975 21.1 13.7 28.8 32.9 48.6 56.9 69.2 61.2 54.1 43.3 29.9 26.0 40.5
1976 24.9 29.5 30.4 43.2 54.1 56.6 67.6 64.8 57.9 44.9 33.8 28.7 44.7
1977 18.0 34.1 32.4 46.9 50.4 63.6 66.3 63.6 56.3 45.6 31.2 20.7 44.1
1978 16.9 22.8 38.8 47.7 53.2 63.2 67.2 65.5 57.9 46.5 22.7 15.2 43.1
1979 1.1 20.1 34.7 42.7 53.2 62.0 69.2 67.7 61.3 47.8 29.0 28.2 43.1
1980 14.3 25.3 31.3 49.0 55.4 59.8 67.3 62.9 56.8 45.4 34.9 26.9 44.1
1981 28.4 29.7 38.0 46.4 52.8 58.9 67.7 69.5 58.8 43.8 36.4 25.3 46.3
1982 16.5 23.7 33.9 40.5 50.9 61.2 68.6 69.1 55.5 44.9 27.4 22.7 42.9
1983 30.6 35.3 38.3 43.1 51.5 60.2 66.0 70.8 53.5 46.0 34.7 5.5 44.6
1984 27.3 32.4 37.2 43.5 52.8 60.0 70.0 69.8 52.3 41.7 33.1 11.6 44.3
1985 12.3 18.8 33.4 46.9 56.2 63.3 75.0 63.1 49.6 42.3 12.6 15.0 40.7
1986 25.5 21.8 42.9 43.3 53.6 66.4 64.2 68.0 51.2 45.3 29.0 18.6 44.2
1987 23.3 31.9 37.0 50.2 55.9 64.4 66.2 62.8 59.9 46.8 34.7 24.7 46.5
1988 18.8 29.1 36.1 47.1 55.5 68.4 71.3 68.6 56.4 50.3 33.8 23.1 46.5
1989 24.5 6.1 27.6 44.5 51.7 62.2 72.0 64.3 55.6 45.1 36.8 23.8 42.9
1990 28.8 26.9 34.9 45.8 51.0 61.5 69.4 68.4 63.6 45.3 37.4 14.0 45.6
1991 19.0 37.5 35.3 43.8 52.8 59.5 70.8 72.8 58.4 43.3 29.8 22.9 45.5
1992 23.7 34.2 42.7 47.7 57.5 64.9 64.3 64.7 56.7 46.7 32.8 14.7 45.9
1993 12.3 15.0 36.4 44.3 57.3 58.5 59.5 61.5 54.0 43.8 26.8 30.0 41.6
1994 29.8 20.7 39.4 45.6 56.2 62.7 69.0 69.9 61.6 44.3 28.3 23.6 45.9
1995 22.7 30.5 30.7 42.0 49.7 57.4 65.8 65.2 55.7 42.8 34.3 22.7 43.3
1996 9.9 21.1 25.7 48.2 61.3 68.3 66.6 55.5 43.8 23.1 16.6
1997 13.3 28.2 36.9 38.4 53.2 60.1 65.8 65.4 58.8 44.1 31.2 24.4 43.3
1998 21.2 31.0 32.8 44.8 53.9 55.1 69.8 68.6 61.9 43.8 34.5 24.5 45.2
1999 26.8 32.4 37.1 40.8 50.2 58.8 65.3 68.4 52.9 45.8 39.2 28.1 45.5
2000 25.0 28.8 38.6 47.0 54.9 62.4 72.1 69.6 56.4 44.6 22.0 16.2 44.8
2001 20.1 17.6 35.4 44.0 59.2 64.1 72.0 74.7 64.6 48.4 39.2 24.5 47.0
POR=121 YRS 19.8 24.7 32.7 43.6 52.4 60.0 67.8 66.4 55.9 45.4 32.3 23.6 43.7

REFERENCE NOTES:

PAGE 1:

THE TEMPERATURE GRAPH SHOWS NORMAL MAXIMUM AND NORMAL MINIMUM DAILY TEMPERATURES (SOLID CURVES) AND THE ACTUAL DAILY HIGH AND LOW TEMPERATURES (VERTICAL BARS).

PAGE 2 AND 3:

H/C INDICATES HEATING AND COOLING DEGREE DAYS.

RH INDICATES RELATIVE HUMIDITY

W/O INDICATES WEATHER AND OBSTRUCTIONS

S INDICATES SUNSHINE.

PR INDICATES PRESSURE.

CLOUDINESS ON PAGE 3 IS THE SUM OF THE CEILOMETER AND SATELLITE DATA NOT TO EXCEED EIGHT EIGHTHS (OKTAS).

GENERAL:

T INDICATES TRACE PRECIPITATION, AN AMOUNT GREATER THAN ZERO BUT LESS THAN THE LOWEST REPORTABLE VALUE.

+ INDICATES THE VALUE ALSO OCCURS ON EARLIER DATES.

BLANK ENTRIES DENOTE MISSING OR UNREPORTED DATA.

NORMALS ARE 30–YEAR AVERAGES (1961–1990).

ASOS INDICATES AUTOMATED SURFACE OBSERVING SYSTEM.

PM INDICATES THE LAST DAY OF THE PREVIOUS MONTH.

POR (PERIOD OF RECORD) BEGINS WITH THE JANUARY DATA MONTH AND IS THE NUMBER OF YEARS USED TO COMPUTE THE MEAN. INDIVIDUAL MONTHS WITHIN THE POR MAY BE MISSING.

WHEN THE POR FOR A NORMAL IS LESS THAN 30 YEARS, THE NORMAL IS PROVISIONAL AND IS BASED ON THE NUMBER OF YEARS INDICATED.

0.* OR * INDICATES THE VALUE OR MEAN–DAYS–WITH IS BETWEEN 0.00 AND 0.05.

CLOUDINESS FOR ASOS STATIONS DIFFERS FROM THE NON–ASOS OBSERVATION TAKEN BY A HUMAN OBSERVER. ASOS STATION CLOUDINESS IS BASED ON TIME–AVERAGED CEILOMETER DATA FOR CLOUDS AT OR BELOW 12,000 FEET AND ON SATELLITE DATA FOR CLOUDS ABOVE 12,000 FEET.

THE NUMBER OF DAYS WITH CLEAR, PARTLY CLOUDY, AND CLOUDY CONDITIONS FOR ASOS STATIONS IS THE SUM OF THE CEILOMETER AND SATELLITE DATA FOR THE SUNRISE TO SUNSET PERIOD.

GENERAL CONTINUED:

CLEAR INDICATES 0–2 OKTAS, PARTLY CLOUDY INDICATES 3–6 OKTAS, AND CLOUDY INDICATES 7 OR 8 OKTAS. WHEN AT LEAST ONE OF THE ELEMENTS (CEILOMETER OR SATELLITE) IS MISSING, THE DAILY CLOUDINESS IS NOT COMPUTED.

WIND DIRECTION IS RECORDED IN TENS OF DEGREES (2 DIGITS) CLOCKWISE FROM TRUE NORTH. "00" INDICATES CALM. "36" INDICATES TRUE NORTH.

RESULTANT WIND IS THE VECTOR AVERAGE OF THE SPEED AND DIRECTION.

AVERAGE TEMPERATURE IS THE SUM OF THE MEAN DAILY MAXIMUM AND MINIMUM TEMPERATURE DIVIDED BY 2.

SNOWFALL DATA COMPRISE ALL FORMS OF FROZEN PRECIPITATION, INCLUDING HAIL.

A HEATING (COOLING) DEGREE DAY IS THE DIFFERENCE BETWEEN THE AVERAGE DAILY TEMPERATURE AND 65 F.

DRY BULB IS THE TEMPERATURE OF THE AMBIENT AIR.

DEW POINT IS THE TEMPERATURE TO WHICH THE AIR MUST BE COOLED TO ACHIEVE 100 PERCENT RELATIVE HUMIDITY.

WET BULB IS THE TEMPERATURE THE AIR WOULD HAVE IF THE MOISTURE CONTENT WAS INCREASED TO 100 PERCENT RELATIVE HUMIDITY.

ON JULY 1, 1996, THE NATIONAL WEATHER SERVICE BEGAN USING THE "METAR" OBSERVATION CODE THAT WAS ALREADY EMPLOYED BY MOST OTHER NATIONS OF THE WORLD. THE MOST NOTICEABLE DIFFERENCE IN THIS ANNUAL PUBLICATION WILL BE THE CHANGE IN UNITS FROM TENTHS TO EIGHTS (OKTAS) FOR REPORTING THE AMOUNT OF SKY COVER.

2001 Helena, Montana (HLN)

HEATING DEGREE DAYS (base 65 F) 2001 HELENA, MT (HLN)
YEAR JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN TOTAL
1972-73 136 49 418 798 1010 1588 1465 1174 892 732 374 155 8791
1973-74 23 47 317 588 1208 1136 1452 897 956 564 500 99 7787
1974-75 16 130 338 588 905 1149 1355 1429 1114 954 501 235 8714
1975-76 14 119 322 666 1045 1199 1236 1023 1064 649 331 257 7925
1976-77 15 45 219 615 928 1120 1449 862 1005 535 443 90 7326
1977-78 52 92 270 593 1008 1367 1485 1175 806 512 361 87 7808
1978-79 32 60 244 564 1263 1540 1979 1250 930 665 359 128 9014
1979-80 11 15 127 528 1072 1138 1566 1148 1039 473 304 164 7585
1980-81 25 81 242 602 899 1175 1127 986 832 552 371 191 7083
1981-82 21 16 195 650 853 1227 1497 1153 959 726 428 136 7861
1982-83 30 16 304 618 1120 1306 1059 828 823 649 417 152 7322
1983-84 76 0 351 584 901 1842 1164 941 856 640 380 174 7909
1984-85 2 7 377 716 954 1654 1625 1291 973 538 266 97 8500
1985-86 3 105 455 696 1571 1545 1218 1202 677 645 380 42 8539
1986-87 66 23 409 602 1077 1432 1288 923 862 437 276 77 7472
1987-88 75 104 163 556 901 1241 1426 1034 889 529 297 63 7278
1988-89 10 13 282 449 934 1292 1251 1650 1156 610 407 107 8161
1989-90 0 92 274 611 839 1268 1116 1058 925 573 426 177 7359
1990-91 15 31 78 604 823 1579 1420 767 914 630 373 159 7393
1991-92 2 0 220 666 1053 1297 1273 884 687 513 237 94 6926
1992-93 68 141 246 564 960 1552 1631 1397 879 617 228 214 8497
1993-94 179 122 323 652 1139 1080 1080 1236 783 576 268 128 7566
1994-95 18 17 110 633 1095 1275 1307 963 1059 681 465 222 7845
1995-96 37 61 293 683 912 1303 1703 1268 1210 510 127
1996-97 15 53 286 651 1251 1494 1596 1026 865 793 361 152 8543
1997-98 49 53 189 642 1006 1252 1352 942 990 600 336 293 7704
1998-99 2 8 158 650 909 1248 1176 905 859 718 451 188 7272
1999-00 79 20 354 590 767 1136 1232 1043 814 535 308 119 6997
2000-01 16 13 279 625 1283 1504 1385 1319 912 625 212 113 8286
2001- 11 0 66 511 766 1249

2001 Helena, Montana (HLN)

COOLING DEGREE DAYS (base 65 F) 2001 HELENA, MT (HLN)
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANNUAL
1972 0 0 0 0 2 30 42 89 0 0 0 0 163
1973 0 0 0 0 4 45 151 108 3 0 0 0 311
1974 0 0 0 0 0 102 190 31 0 0 0 0 323
1975 0 0 0 0 0 1 154 12 0 0 0 0 167
1976 0 0 0 0 0 14 102 45 10 0 0 0 171
1977 0 0 0 0 0 57 101 54 13 0 0 0 225
1978 0 0 0 0 3 37 109 85 37 0 0 0 271
1979 0 0 0 0 1 45 152 103 21 0 0 0 322
1980 0 0 0 0 14 14 104 25 4 0 0 0 161
1981 0 0 0 0 0 15 109 165 16 0 0 0 305
1982 0 0 0 0 0 30 147 151 25 0 0 0 353
1983 0 0 0 0 4 16 115 186 12 0 0 0 333
1984 0 0 0 0 10 31 165 163 4 0 0 0 373
1985 0 0 0 0 2 55 318 54 0 0 0 0 429
1986 0 0 0 0 35 91 45 123 1 0 0 0 295
1987 0 0 0 0 3 66 122 41 15 0 0 0 247
1988 0 0 0 0 8 170 211 132 30 0 0 0 551
1989 0 0 0 0 0 30 222 82 0 0 0 0 334
1990 0 0 0 0 0 77 159 142 42 0 0 0 420
1991 0 0 0 0 0 2 188 250 29 0 0 0 469
1992 0 0 0 0 10 96 55 140 3 0 0 0 304
1993 0 0 0 0 2 24 15 23 0 0 0 0 64
1994 0 0 0 0 1 67 146 176 16 0 0 0 406
1995 0 0 0 0 0 5 71 73 24 0 0 0 173
1996 0 0 0 0 25 125 109 9 0 0 0
1997 0 0 0 0 1 13 81 71 12 0 0 0 178
1998 0 0 0 0 0 0 161 124 72 0 0 0 357
1999 0 0 0 0 0 10 93 132 0 0 0 0 235
2000 0 0 0 0 2 50 245 165 27 0 0 0 489
2001 0 0 0 0 41 94 237 308 61 0 0 0 741

2001 Helena, Montana (HLN)

SNOWFALL (inches) 2001 HELENA, MT (HLN)
YEAR JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN TOTAL
1972-73 T 0.0 0.3 4.7 0.7 7.8 3.2 1.8 0.1 6.5 T 0.0 25.1
1973-74 0.0 0.0 1.3 7.2 12.5 7.2 9.9 5.9 2.2 1.5 0.2 0.0 47.9
1974-75 0.0 0.0 T 1.5 0.8 2.7 15.2 10.7 12.3 15.4 0.2 0.0 58.8
1975-76 0.0 0.0 0.0 6.3 4.9 3.9 3.3 4.4 6.7 10.9 0.0 0.0 40.4
1976-77 0.0 0.0 0.0 T 2.9 0.9 13.8 0.8 14.1 0.5 1.0 0.0 34.0
1977-78 0.0 0.0 0.0 0.4 6.8 19.5 15.7 13.3 2.6 0.9 T 0.0 59.2
1978-79 0.0 0.0 T T 22.1 13.8 11.7 7.2 12.4 9.3 T T 76.5
1979-80 0.0 0.0 0.0 0.2 0.6 6.5 9.3 10.5 10.1 3.1 0.0 0.0 40.3
1980-81 0.0 0.0 0.0 3.7 1.2 3.8 2.7 2.1 3.3 0.1 T 0.0 16.9
1981-82 0.0 0.0 0.0 5.2 3.4 6.1 18.4 4.8 13.9 4.1 0.8 0.0 56.7
1982-83 0.0 0.0 6.5 0.5 4.1 11.3 3.2 0.2 2.2 1.1 9.9 0.0 39.0
1983-84 0.0 0.0 6.4 0.0 1.3 13.0 1.3 1.5 5.7 2.3 0.8 0.0 32.3
1984-85 0.0 0.0 6.3 9.0 5.7 7.5 3.9 6.2 4.0 0.8 0.0 0.0 43.4
1985-86 0.0 0.0 2.9 8.8 10.4 8.5 4.2 15.6 1.2 11.6 0.2 0.0 63.4
1986-87 0.0 0.0 0.0 T 7.6 5.0 0.2 0.2 9.1 4.3 3.8 0.0 30.2
1987-88 0.0 0.0 0.0 0.3 0.9 1.2 4.4 8.0 5.2 2.9 0.0 0.0 22.9
1988-89 0.0 0.0 5.9 1.5 6.0 5.0 23.0 13.0 20.7 7.9 3.5 T 86.5
1989-90 0.0 T T 2.6 1.8 9.4 4.3 1.8 14.0 0.8 0.1 0.0 34.8
1990-91 0.0 0.5 0.0 0.5 8.6 11.6 5.9 0.8 12.2 5.6 0.4 0.5 46.6
1991-92 0.0 T 0.0 7.3 8.8 15.7 4.7 1.3 T 2.2 T 0.0 40.0
1992-93 T 6.2 T 8.6 1.5 11.8 10.2 17.9 2.3 2.5 T 0.2 61.2
1993-94 T 0.0 T 4.6 7.3 1.1 4.4 5.0 4.4 8.0 T 0.0 34.8
1994-95 0.0 T 0.0 T 8.6 2.0 0.3 1.6 8.1 0.0 0.0
1995-96 T 0.0 T 7.4 2.7 14.2
1996-97
1997-98
1998-99
1999-00 T 3.9 5.7 2.3
2000-01
2001-
POR=56 YRS T 0.1 1.5 2.3 6.3 8.2 8.6 6.0 7.3 4.8 1.4 0.1 46.6



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