2001 Denver, Colorado (DEN)

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2001 DENVER, COLORADO (DEN)

Denver enjoys the invigorating climate that prevails over much of the central Rocky Mountain region, without the extremely cold mornings of the high elevations during winter, or the hot afternoons of summer at lower altitudes. Extremely warm or cold weather in Denver is usually of short duration.

Situated a long distance from any moisture source, and separated from the Pacific Ocean by several high mountain barriers, Denver enjoys low relative humidity, light precipitation, and abundant sunshine.

Air masses from four different sources influence Denver weather. These include arctic air from Canada and Alaska, warm, moist air from the Gulf of Mexico, warm, dry air from Mexico and the southwestern deserts, and Pacific air modified by its passage over mountains to the west.

In winter, the high altitude and mountains to the west combine to moderate temperatures in Denver. Invasions of cold air from the north, intensified by the high altitude, can be abrupt and severe. However, many of the cold air masses that spread southward out of Canada never reach the altitude of Denver, but move off over the lower plains to the east. Surges of air from the west are moderated in their descent down the east face of the Rockies, and reach Denver in the form of chinook winds that often raise temperatures into the 60s, even in midwinter.

In spring, polar air often collides with warm, moist air from the Gulf of Mexico and these collisions result in frequent, rapid and drastic weather changes. Spring is the cloudiest, windiest, and wettest season in the city. Much of the precipitation falls as snow, especially in March and early April. Stormy periods are interspersed with stretches of mild, sunny weather that quickly melt previous snow cover.

Summer precipitation falls mainly from scattered thunderstorms during the afternoon and evening. Mornings are usually clear and sunny, with clouds forming during early afternoon to cut off the sunshine at what would otherwise be the hottest part of the day. Severe thunderstorms, with large hail and heavy rain occasionally occur in the city, but these conditions are more common on the plains to the east.

Autumn is the most pleasant season. Few thunderstorms occur and invasions of cold air are infrequent. As a result, there is more sunshine and less severe weather than at any other time of the year.

Based on the 1951–1980 period, the average first occurrence of 32 degrees Fahrenheit in the fall is October 8 and the average last occurrence in the spring is May 3.

NORMALS, MEANS, AND EXTREMES

DENVER, CO (DEN)

LATITUDE:    LONGITUDE:    ELEVATION (FT):    TIME ZONE:    WBAN: 03017

39 49′ 58″ N  104 39′ 27″ W  GRND: 5379  BARO: 5382  MOUNTAIN (UTC + 7)

ELEMENTPORJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECYEAR
TEMPERATURE FNORMAL DAILY MAXIMUM3042.546.352.261.470.781.288.185.676.666.352.043.963.9
MEAN DAILY MAXIMUM643.447.153.958.970.080.788.686.677.764.752.343.263.9
HIGHEST DAILY MAXIMUM67269798493981019997877872101
YEAR OF OCCURRENCE199719991997199619962001200119951995199719991998JUL 2001
MEAN OF EXTREME MAXS.665.765.574.578.086.993.799.095.692.483.471.762.780.8
NORMAL DAILY MINIMUM3013.818.323.732.041.250.156.054.245.134.223.415.333.9
MEAN DAILY MINIMUM617.920.925.632.142.751.259.658.449.336.325.718.536.5
LOWEST DAILY MINIMUM6-14-16-2623344442253-3-19-19
YEAR OF OCCURRENCE199719961996199720001998199719951996199719971998DEC 1998
MEAN OF EXTREME MINS.6-2.42.77.716.830.039.950.749.632.320.14.90.321.1
NORMAL DRY BULB3028.232.338.046.855.965.672.169.861.050.237.629.648.9
MEAN DRY BULB630.734.039.745.456.566.074.172.563.550.539.030.950.2
MEAN WET BULB625.127.627.631.940.246.059.358.951.040.431.525.438.7
MEAN DEW POINT615.116.321.127.238.844.349.550.241.128.921.115.530.8
NORMAL NO. DAYS WITH:
MAXIMUM 90
MAXIMUM 32
MINIMUM 32
MINIMUM 0
H/CNORMAL HEATING DEG. DAYS3011419168375462888401116245982210976363
NORMAL COOLING DEG. DAYS300000610222416042000534
RHNORMAL (PERCENT)
HOUR 05 LST
HOUR 11 LST
HOUR 17 LST
HOUR 23 LST
SPERCENT POSSIBLE SUNSHINE
W/OMEAN NO. DAYS WITH:
HEAVY FOG (VISBY 1/4 MI)62.33.03.52.82.21.21.71.51.52.21.91.225.0
THUNDERSTORMS60.00.20.82.47.310.814.511.45.60.70.00.053.7
CLOUDINESSMEAN:
SUNRISE-SUNSET (OKTAS)15.05.37.25.62.52.52.5
MIDNIGHT-MIDNIGHT (OKTAS)15.37.26.43.02.0
MEAN NO. DAYS WITH:
CLEAR13.010.09.06.010.012.02.07.06.09.013.0
PARTLY CLOUDY14.02.06.04.05.59.02.09.06.01.0
CLOUDY13.06.010.013.05.55.01.03.05.02.02.0
PRMEAN STATION PRESSURE (IN)624.5324.5624.5624.5424.5624.6124.6924.7024.6624.6124.6024.5724.60
MEAN SEA-LEVEL PRES. (IN)629.9929.9929.9329.8829.8429.8329.8829.9229.9429.9530.0130.0429.93
WINDSMEAN SPEED (MPH)69.49.710.311.310.510.49.79.49.39.89.39.99.9
PREVAIL. DIR (TENS OF DEGS)520212101211621212221222121
MAXIMUM 2-MINUTE:
SPEED (MPH)641465353494954493946454754
DIR. (TENS OF DEGS)28262833363013280229273013
YEAR OF OCCURRENCE199620001995200120011999199920012001200120001997JUL 1999
MAXIMUM 5-SECOND:
SPEED (MPH)648545660586364614954545364
DIR. (TENS OF DEGS)29263233012913290229282913
YEAR OF OCCURRENCE199620001997200120011999199920012001200120002000JUL 1999
PRECIPITATIONNORMAL (IN)300.500.541.261.682.622.051.991.651.340.990.890.6016.11
MAXIMUM MONTHLY (IN)60.780.641.965.864.673.075.923.522.341.870.720.505.92
YEAR OF OCCURRENCE200120012000199919951995199819971996199720011997JUL 1998
MINIMUM MONTHLY (IN)60.050.090.190.331.570.731.010.560.730.080.310.060.05
YEAR OF OCCURRENCE199819961999199619971998199619961998200119951995JAN 1998
MAXIMUM IN 24 HOURS (IN)60.510.300.632.062.001.153.061.461.221.120.470.193.06
YEAR OF OCCURRENCE200120011996199920001999199720001996199719991997JUL 1997
NORMAL NO. DAYS WITH:
PRECIPITATION 0.01
PRECIPITATION 1.00
SNOWFALLNORMAL (IN)
MAXIMUM MONTHLY (IN)
YEAR OF OCCURRENCE
MAXIMUM IN 24 HOURS (IN)
YEAR OF OCCURRENCE
MAXIMUM SNOW DEPTH (IN)
YEAR OF OCCURRENCE
NORMAL NO. DAYS WITH:
SNOWFALL 1.0
PRECIPITATION (inches) 2001 DENVER, CO (DEN)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
19950.282.444.673.072.311.042.280.720.310.06
19960.290.090.770.332.401.771.010.562.340.390.380.0610.39
19970.260.540.261.301.572.575.603.520.971.870.610.5019.57
19980.050.230.862.471.730.735.921.190.731.200.400.4215.93
19990.380.150.195.862.372.523.843.371.200.310.470.2920.95
20000.240.231.960.713.090.791.423.061.520.520.610.2714.42
20010.780.641.101.203.801.534.760.711.000.080.720.1416.46
POR=6 YRS0.340.320.822.162.691.763.872.121.300.850.520.2917.04
AVERAGE TEMPERATURE (F) 2001 DENVER, (DEN)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
199539.342.950.062.270.975.361.748.541.833.0
199627.033.936.048.058.168.273.471.660.850.937.233.049.8
199727.930.042.140.556.667.873.169.764.349.734.827.948.7
199832.733.936.944.859.163.074.371.768.050.242.128.950.5
199933.738.643.742.654.864.273.971.259.252.547.333.851.3
200033.039.240.449.859.267.076.774.563.650.528.928.350.9
200130.028.339.849.657.169.476.773.566.851.540.931.751.3
POR=6 YRS30.734.040.145.556.966.174.572.363.950.838.930.750.4

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 DENVER, CO (DEN)
YEARJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNTOTAL
1994-95788655457132
1995-9626218850568698111668948932302905600
1996-97041924448249851142975704728264356297
1997-982119247589511429968658655971861376263
1998-9911464536801113962731654666311855703
1999-0013194383528962984744754446215615275
2000-01051494471074113110791021775455256466438
2001-04654167171026
COOLING DEGREE DAYS (base 65 F) 2001 DENVER, CO (DEN)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
19950005521232798000
1996000326133269215711300730
199700001112626016077800642
199800001388296215143000755
1999000026928320330200589
2000000043127368305115500963
2001000018184373274125500979
SNOWFALL (inches) 2001 DENVER, CO (DEN)
YEARJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNTOTAL
POR=

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