2001 Cheyenne, Wyoming (CYS)

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2001 CHEYENNE, WYOMING (CYS)

The city of Cheyenne is located on a broad plateau between the North and South Platte Rivers in the extreme southeastern corner of Wyoming at an elevation of approximately 6,100 feet. The surrounding country is mostly rolling prairie which is used primarily for grazing. The ground level rises rapidly to a ridge approximately 9,000 feet in elevation about 30 miles west of the city. This ridge is known as the Laramie Mountains, one of the ranges of the Rockies, and extends in a north–south direction. Because of this ridge, winds from the northwest through west to southwest are downslope and produce a marked chinook effect in Cheyenne which is especially noticeable during the winter months. Also, winds from the north through east to south are upslope and may cause fog or low stratus clouds in the Cheyenne area throughout the year. Because of this terrain variation, the wind direction plays an important role in controlling the local temperature and weather.

Cheyenne experiences large diurnal and annual temperature ranges. This is due to the advent of both warm and cold air masses and the relatively high elevation of the city which permits rapid incoming and outgoing radiation. The daily temperature range averages about 30 degrees in the summer and 23 degrees in the winter. Many cold air masses from the north during the winter months miss Cheyenne. Because of the downslope of land to the east and the prevailing westerlies, some of the cold air masses do move over the city, but only about 13 percent of the days in an average January, the coldest month of the year, show temperatures dropping to zero or below. Temperatures during the winter months average a few degrees higher than over the Mississippi and Missouri Valleys at the same latitude.

Windy days are quire frequent during the winter and spring months. Since the wind is usually strongest during the daytime it is a very noticeable weather element. Usually the strong winds are from a westerly direction and this tends to raise the temperature because the air is moving downslope.

Most of the air masses reaching this area move in from the Pacific and since the mountains to the west are quite effective moisture barriers the climate is semi–arid. Fortunately, about 70 percent of normal annual precipitation occurs during the growing season. In the summer months, precipitation is mostly of the shower type and occurs mainly with thunderstorms. Hail is frequent and occasionally destructive in some thunderstorms. Most of the snow falls during the late winter and early spring months. It is not uncommon to have heavy snow in May.

The growing season in Cheyenne averages about 132 days a year and extends from around May 18th to September 27th. Freezing temperatures have occurred as late in the spring as mid–June, and as early in the fall as late August.

Relative humidity averages near 50 percent on an annual basis with large daily variations. Very seldom is the relative humidity above 30 percent when the temperature is above 80 degrees.

NORMALS, MEANS, AND EXTREMES

CHEYENNE, WY (CYS)

LATITUDE: LONGITUDE: ELEVATION (FT): TIME ZONE: WBAN: 24018

41 09′ 28″ N  104 48′ 25″ W GRND: 6125 BARO: 6128 MOUNTAIN (UTC + 7)

ELEMENTPORJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECYEAR
TEMPERATURE FNORMAL DAILY MAXIMUM3037.740.544.954.764.674.482.280.071.160.046.838.858.0
MEAN DAILY MAXIMUM5437.940.644.954.364.575.181.179.470.559.245.539.057.7
HIGHEST DAILY MAXIMUM6666717483911001009695837569100
YEAR OF OCCURRENCE198219621986199220001954193919791995199219991939JUN 1954
MEAN OF EXTREME MAXS.5456.959.165.173.981.389.291.189.384.776.464.757.674.1
NORMAL DAILY MINIMUM3015.218.122.130.139.448.354.652.843.733.923.716.733.2
MEAN DAILY MINIMUM5415.418.121.829.939.648.453.552.243.133.122.917.132.9
LOWEST DAILY MINIMUM66-29-34-21-8162538368-1-16-28-34
YEAR OF OCCURRENCE198419361943197519471951195219751985199119931990FEB 1936
MEAN OF EXTREME MINS.54-8.8-3.92.014.027.737.745.043.629.617.32.7-5.416.8
NORMAL DRY BULB3026.529.333.642.552.061.368.466.457.447.035.227.845.6
MEAN DRY BULB5426.729.333.442.152.161.667.365.856.846.034.228.045.3
MEAN WET BULB1822.823.729.435.244.651.852.952.644.635.526.221.436.7
MEAN DEW POINT1812.914.820.126.236.343.444.344.735.826.017.312.127.8
NORMAL NO. DAYS WITH:
MAXIMUM 90300.00.00.00.0*1.35.22.10.10.00.00.08.7
MAXIMUM 32309.37.05.41.4*0.00.00.00.20.74.18.937.0
MINIMUM 323028.826.127.718.03.60.00.00.02.112.224.428.5171.4
MINIMUM 0304.42.51.00.10.00.00.00.00.00.00.53.411.9
H/CNORMAL HEATING DEG. DAYS3011941000973675403150314425155889411537326
NORMAL COOLING DEG. DAYS3000000391368723000285
RHNORMAL (PERCENT)3052555654565451515250545453
HOUR 05 LST3057616568717170696761605865
HOUR 11 LST3045464643424036363838434642
HOUR 17 LST3049484742444138383841505244
HOUR 23 LST3058616465676463636259605962
SPERCENT POSSIBLE SUNSHINE6264676763616769687069616066
W/OMEAN NO. DAYS WITH:
HEAVY FOG(VISBY 1/4 MI)671.01.93.23.33.01.91.21.41.92.01.91.424.1
THUNDERSTORMS670.00.00.22.17.811.313.210.54.50.90.00.050.5
CLOUDINESSMEAN:
SUNRISE-SUNSET (OKTAS)14.86.47.24.04.0
MIDNIGHT-MIDNIGHT (OKTAS)17.24.0
MEAN NO. DAYS WITH:
CLEAR14.07.05.04.013.0
PARTLY CLOUDY13.06.05.012.08.0
CLOUDY13.04.011.013.07.0
PRMEAN STATION PRESSURE(IN)2923.9023.8923.8023.9023.9024.0024.1124.1124.1024.0123.9123.9123.96
MEAN SEA-LEVEL PRES. (IN)1830.0630.0429.9729.9229.8829.9829.9629.9930.0030.0330.0330.0829.99
WINDSMEAN SPEED (MPH)4415.214.714.414.112.611.410.410.411.212.313.514.612.9
PREVAIL. DIR (TENS OF DEGS)2228292828282828282828282828
MAXIMUM 2-MINUTE:
SPEED (MPH)655594855445146564853596363
DIR. (TENS OF DEGS)25272830282720252826272727
YEAR OF OCCURRENCE200019991999199919971998200119962000200119991998DEC 1998
MAXIMUM 5-SECOND:
SPEED (MPH)664716069556159606063687575
DIR. (TENS OF DEGS)26272932252832252226272626
YEAR OF OCCURRENCE199919992000199919992001199619962000200119991998DEC 1998
PRECIPITATIONNORMAL (IN)300.400.391.031.372.392.082.091.691.270.740.530.4214.40
MAXIMUM MONTHLY (IN)662.782.163.655.046.005.325.016.644.523.572.481.686.64
YEAR OF OCCURRENCE194919531990194219951955197319851973194219791937AUG 1985
MINIMUM MONTHLY (IN)66TT0.120.340.110.070.580.030.010.03T0.03T
YEAR OF OCCURRENCE195219831966199219741980196919441992196419651959FEB 1983
MAXIMUM IN 24 HOURS (IN)661.411.601.881.942.072.683.426.062.751.701.661.196.06
YEAR OF OCCURRENCE194919531946198419911955197319851973194719791979AUG 1985
NORMAL NO. DAYS WITH:
PRECIPITATION 0.01305.16.09.29.311.310.210.89.67.55.66.06.096.6
PRECIPITATION 1.0030*0.00.00.10.40.20.20.10.20.0**1.2
SNOWFALLNORMAL (IN)306.05.412.47.93.0T0.00.00.84.16.46.552.5
MAXIMUM MONTHLY (IN)6635.523.339.231.830.48.71.00.511.821.331.121.339.2
YEAR OF OCCURRENCE198019951990198419431947199419932000196919791958MAR 1990
MAXIMUM IN 24 HOURS (IN)6612.714.015.617.415.08.71.00.510.18.619.811.719.8
YEAR OF OCCURRENCE199219531973198419421947199419932000199019791979NOV 1979
MAXIMUM SNOW DEPTH (IN)532312191512000810261726
YEAR OF OCCURRENCE198019891990198419782000199019791979NOV 1979
NORMAL NO. DAYS WITH:
SNOWFALL 1.0301.91.73.62.10.70.00.00.00.31.32.02.015.6
PRECIPITATION (inches) 2001 CHEYENNE, WY (CYS)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
19720.360.020.790.802.761.711.351.831.010.420.590.4012.04
19730.230.071.851.750.311.205.010.274.520.061.251.0617.58
19740.480.031.240.500.112.811.411.290.500.910.490.109.87
19750.400.171.170.472.271.492.620.390.520.490.200.5210.71
19760.320.710.321.792.070.682.391.400.770.150.280.1010.98
19770.140.081.211.862.502.443.491.070.190.080.350.2413.65
19780.580.780.350.523.980.630.981.380.120.500.450.5410.81
19790.270.141.340.772.903.321.831.860.320.462.481.5017.19
19802.710.731.360.932.390.072.001.550.970.510.460.0813.76
19810.300.200.700.735.671.662.852.900.310.850.090.4516.71
19820.410.190.170.533.564.522.711.812.871.200.430.8319.23
19830.02T2.964.452.312.812.121.950.780.492.340.4620.69
19840.540.841.283.710.782.432.572.840.651.550.110.3417.64
19850.660.190.361.101.051.593.996.641.780.940.840.8019.94
19860.130.500.542.261.032.421.041.552.471.780.660.1814.56
19870.090.901.250.684.431.802.041.230.930.330.760.8515.29
19880.520.651.341.843.092.031.791.791.660.090.420.5315.75
19890.271.260.490.481.372.511.701.791.620.410.140.6912.73
19900.350.693.651.663.371.033.641.980.801.350.720.3919.63
19910.360.120.431.153.844.563.391.491.870.440.870.1318.65
19921.180.111.750.341.862.111.871.900.010.461.690.4913.77
19930.350.810.632.491.923.320.642.213.161.851.230.3018.91
19940.660.880.551.452.051.442.131.490.381.550.340.5713.49
19950.121.020.191.496.004.581.080.893.390.780.370.1820.09
19960.500.071.501.512.241.793.101.792.340.500.450.0115.80
19970.390.310.441.682.473.482.804.332.061.090.200.5919.84
19980.070.290.691.092.351.631.210.960.491.270.310.4610.82
19990.350.130.465.022.042.132.380.782.110.270.250.1916.11
20000.350.591.480.581.380.462.641.872.640.690.300.7513.73
20010.410.330.562.492.241.453.310.741.180.400.230.1313.47
POR=130 YRS0.430.551.051.762.461.882.031.521.240.800.500.4114.63
AVERAGE TEMPERATURE (F) 2001 CHEYENNE, WY (CYS)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
197225.333.239.342.551.263.264.364.656.645.529.521.044.7
197323.729.731.937.351.462.965.868.454.149.335.329.444.9
197424.131.937.143.355.064.170.165.255.348.335.626.646.4
197525.525.030.237.548.457.967.366.356.048.134.232.644.1
197626.932.930.942.751.159.769.265.057.743.433.530.645.3
197722.432.932.144.753.465.268.263.560.748.334.429.046.2
197822.125.037.743.949.061.068.764.359.647.933.521.144.5
197917.331.636.044.949.961.569.965.962.949.829.532.946.0
198022.229.433.042.351.265.571.466.560.446.736.838.547.0
198133.432.236.850.150.563.769.065.261.246.140.730.748.3
198225.528.236.141.850.557.567.769.156.745.131.428.344.8
198332.833.532.034.847.457.367.870.259.048.632.315.044.2
198424.328.432.435.753.659.468.466.653.040.035.027.043.7
198519.523.335.245.654.361.169.366.852.845.126.226.143.8
198637.030.142.243.950.664.568.567.055.344.634.328.747.2
198729.131.632.446.754.563.369.264.958.046.936.725.746.6
198821.528.432.344.453.367.469.768.757.550.335.328.746.5
198930.217.337.444.354.360.370.667.057.546.538.724.345.7
199031.528.731.942.849.364.165.066.462.246.738.720.845.7
199125.036.236.441.152.462.567.767.758.046.131.731.646.4
199230.536.738.648.655.060.864.663.860.049.230.925.547.0
199326.124.937.242.153.458.766.164.854.344.129.230.744.3
199429.427.238.643.356.966.368.069.461.746.934.633.348.0
199530.732.636.839.545.759.067.871.657.145.838.430.046.3
199623.030.231.642.751.763.668.366.356.645.834.730.145.4
199724.726.738.335.951.762.668.365.059.246.131.428.344.9
199830.630.632.741.253.356.870.368.764.045.839.526.646.7
199930.834.637.638.450.560.370.067.754.047.644.032.047.3
200029.834.737.145.455.562.572.270.558.246.325.925.347.0
200127.626.935.144.352.664.272.269.561.547.238.929.247.4
POR=128 YRS26.228.132.841.651.161.167.866.457.546.435.028.445.2

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.

HEATING DEGREE DAYS (base 65 F) 2001 CHEYENNE, WY (CYS)
YEARJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNTOTAL
1972-73857524859910561358127598010178244141228053
1973-74804323482883109812649228626433041106975
1974-7545530250987311801215111510708195062127860
1975-761139274515920998117592410486614251587148
1976-771144224664937105913148941014602352447159
1977-7821741505119101108132411158406274911577328
1978-792873200523937135814719338935974591397611
1979-80262105468105899013211027984673424657179
1980-81041151558840812974913868440445956137
1981-8221501205807221058121610258926874462277044
1982-832972646081002113199287510168985382337593
1983-8423020250297415471259105810028703481777962
1984-856153657698921171140311639175763231627762
1985-86113736461211581199862970698629440717051
1986-87420286630914112111029281002542321786948
1987-8827792145548411213134310561008611361427349
1988-8912182364498841116107513328516153341807102
1989-9041823656677912571037101210216624801067178
1990-91752812755878413641231799879712385957037
1991-922617217586993103110628138114883071316482
1992-93639216148410141216119811188566803512027435
1993-9445583226421068105910971053809644249437089
1994-95241613155290497810579018667585881996974
1995-963762835897931076129310021031663411777261
1996-9716292695909051076124210658208674001027381
1997-9834581815771001113010599579947063522567305
1998-99710104587754118310558458407914441506770
1999-00827322534625101510838708585813051306358
2000-012824257311671223115510649226143771067453
2001-0111355457761102
COOLING DEGREE DAYS (base 65 F) 2001 CHEYENNE, WY (CYS)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
1972000001169692000151
197300000651121160000293
197400004881736717000349
1975000007908610000193
19760000071455015000217
197700000591263829000252
197800001431505944000297
1979000014216010049000352
198000000882059421000408
198100000591566415000294
198200000812014021000289
1983000001011516928000322
19840000114118728000213
19850000052150988000308
19860000062118890000269
19870000035164839000291
19880000412216614018000450
198900007461888619000346
19900000086847949000298
1991000022811910613400272
19920001215586316000155
1993000001989606000174
1994000039112515638000413
1995000002313221850000423
199600002401247324000263
199700000371446513000259
1998000001718213178000408
199900000181701140000302
20000000195923118744000540
2001000009122915838000516
SNOWFALL (inches) 2001 CHEYENNE, WY (CYS)
YEARJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNTOTAL
1972-730.00.0T5.08.87.64.60.627.012.81.20.067.6
1973-740.00.0T0.517.413.95.00.816.38.00.00.061.9
1974-750.00.01.91.42.41.55.84.314.05.40.80.037.5
1975-760.00.00.65.54.78.46.08.59.06.7TT49.4
1976-770.00.00.01.53.51.22.50.812.97.0T0.029.4
1977-780.00.00.00.44.35.67.012.02.51.018.30.051.1
1978-790.00.00.12.09.317.66.72.221.14.014.1T77.1
1979-800.00.00.03.631.115.635.510.717.83.43.80.0121.5
1980-810.00.00.01.16.32.13.42.99.02.00.80.027.6
1981-820.00.00.04.60.85.85.62.41.72.04.00.026.9
1982-830.00.00.012.27.913.10.1T31.925.710.10.0101.0
1983-840.00.0T0.227.27.07.912.113.031.8T0.099.2
1984-850.00.01.63.81.55.69.81.93.62.60.40.030.8
1985-860.00.07.46.012.413.01.34.95.611.33.80.065.7
1986-870.00.00.09.26.92.21.19.913.74.4T0.047.4
1987-880.00.00.01.34.516.19.07.516.07.52.20.064.1
1988-890.00.00.20.04.57.24.417.65.04.3TT43.2
1989-90TT2.63.41.99.75.611.639.25.61.3T80.9
1990-91TTT12.38.86.67.71.63.710.5TT51.2
1991-92TTT7.59.12.018.20.811.30.74.40.554.5
1992-93TT0.02.125.510.97.114.66.611.3T0.578.6
1993-940.00.55.53.118.05.711.516.14.29.1TT73.7
1994-951.00.00.92.33.010.02.723.34.413.22.6T63.4
1995-960.00.03.06.46.43.611.92.121.98.70.1T64.1
1996-97TT1.22.07.00.410.57.98.423.32.8T63.5
1997-98TTT8.82.510.91.33.48.410.11.10.747.2
1998-99T0.00.00.34.013.56.42.44.917.00.9T49.4
1999-000.00.03.73.34.32.92.910.716.21.70.20.045.9
2000-01TT11.80.74.313.58.66.87.023.213.1T89.0
2001-T0.0T2.64.32.1
POR=65 YRS0.00.01.13.77.16.36.46.311.59.33.50.255.4

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2001 Cheyenne, Wyoming (CYS)