2001 Raleigh, North Carolina (RDU)

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2001 RALEIGH, NORTH CAROLINA (RDU)

The Raleigh–Durham Airport is located in the zone of transition between the Coastal Plain and the Piedmont Plateau. The surrounding terrain is rolling, with an average elevation of around 400 feet, the range over a 10–mile radius is roughly between 200 and 550 feet. Being centrally located between the mountains on the west and the coast on the south and east, the Raleigh–Durham area enjoys a favorable climate. The mountains form a partial barrier to cold air masses moving eastward from the interior of the nation. As a result, there are few days in the heart of the winter season when the temperature falls below 20 degrees. Tropical air is present over the eastern and central sections of North Carolina during much of the summer season, bringing warm temperatures and rather high humidities to the Raleigh–Durham area. Afternoon temperatures reach 90 degrees or higher on about one–fourth of the days in the middle of summer, but reach 100 degrees less than once per year. Even in the hottest weather, early morning temperatures almost always drop into the lower 70s.

Rainfall is well distributed throughout the year as a whole. July and August have the greatest amount of rainfall, and October and November the least. There are times in spring and summer when soil moisture is scanty. This usually results from too many days between rains rather than from a shortage of total rainfall, but occasionally the accumulated total during the growing season falls short of plant needs. Most summer rain is produced by thunderstorms, which may occasionally be accompanied by strong winds, intense rains, and hail. The Raleigh–Durham area is far enough from the coast so that the bad weather effects of coastal storms are reduced. While snow and sleet usually occur each year, excessive accumulations of snow are rare.

From September 1887 to December 1950, the office was located in the downtown areas of Raleigh. The various buildings occupied were within an area of three blocks. All thermometers were exposed on the roof, and this, plus the smoke over the city, had an effect on the temperature record of that period. Lowest temperatures at the city office were frequently from 2 to 5 degrees higher than those recorded in surrounding rural areas. Maximum temperatures in the city were generally a degree or two lower. These observations are supported by a period of simultaneous record from the Municipal Airport and the city office location between 1937 and 1940.

From September 1946 to May 1954, simultaneous records were kept at a surface location on the North Carolina State College campus in Raleigh, and at the Raleigh–Durham Airport 10 l/2 air miles to the northwest.

Based on the 1951–1980 period, the average first occurrence of 32 degrees Fahrenheit in the fall is October 27 and the average last occurrence in the spring is April 11.

NORMALS, MEANS, AND EXTREMES

RALEIGH, NC (RDU)

LATITUDE:    LONGITUDE:    ELEVATION (FT):    TIME ZONE:    WBAN: 13722

35 52′ 14″ N  78 47′ 11″ W  GRND:  427  BARO:  430  EASTERN (UTC + 5)

ELEMENTPORJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECYEAR
TEMPERATURE FNORMAL DAILY MAXIMUM3048.952.662.171.778.685.088.086.881.171.662.652.770.1
MEAN DAILY MAXIMUM5450.553.961.771.979.085.688.787.481.371.962.453.170.6
HIGHEST DAILY MAXIMUM577984929597104105105104988880105
YEAR OF OCCURRENCE195219771945198019531954195219881954195419501998AUG 1988
MEAN OF EXTREME MAXS.5470.773.681.087.590.495.696.595.591.885.378.572.184.9
NORMAL DAILY MINIMUM3028.831.338.746.255.363.668.167.561.148.439.732.448.4
MEAN DAILY MINIMUM5429.831.838.146.655.463.668.066.860.448.138.832.048.3
LOWEST DAILY MINIMUM57-901123313848463719114-9
YEAR OF OCCURRENCE198519961980198519771977197519651983196219701983JAN 1985
MEAN OF EXTREME MINS.5411.715.122.330.440.550.857.155.545.531.522.514.733.1
NORMAL DRY BULB3038.942.050.459.067.074.378.177.171.160.151.242.659.3
MEAN DRY BULB5440.143.050.059.267.274.578.577.171.060.050.642.559.5
MEAN WET BULB1836.339.444.452.160.668.268.166.761.254.946.436.352.9
MEAN DEW POINT1828.931.536.345.052.564.665.264.058.150.340.329.647.2
NORMAL NO. DAYS WITH:
MAXIMUM 90300.00.0*0.61.56.911.910.13.00.20.00.034.2
MAXIMUM 32302.40.60.10.00.00.00.00.00.00.0*0.83.9
MINIMUM 323020.817.49.52.30.10.00.00.00.01.69.117.878.6
MINIMUM 0300.20.00.00.00.00.00.00.00.00.00.00.00.2
H/CNORMAL HEATING DEG. DAYS308096444581934700091894146943457
NORMAL COOLING DEG. DAYS300061310927940637519237001417
RHNORMAL (PERCENT)3066646362717476787773696870
HOUR 01 LST3073717173848788908885787580
HOUR 07 LST3079788080858789929289848085
HOUR 13 LST3054524945535658595852525554
HOUR 19 LST3063595653656770747674676666
SPERCENT POSSIBLE SUNSHINE4252566063596060585860575358
W/OMEAN NO. DAYS WITH:
HEAVY FOG(VISBY 1/4 MI)523.52.82.11.42.31.92.63.23.33.33.23.433.0
THUNDERSTORMS570.40.92.13.56.27.210.47.73.31.40.80.344.2
CLOUDINESSMEAN:
SUNRISE-SUNSET (OKTAS)475.04.74.74.44.74.64.84.74.73.94.24.64.6
MIDNIGHT-MIDNIGHT (OKTAS)324.74.44.34.14.64.44.74.64.23.74.04.34.3
MEAN NO. DAYS WITH:
CLEAR489.08.79.49.68.27.67.27.39.512.811.310.0110.6
PARTLY CLOUDY486.76.17.39.110.011.812.212.39.17.17.37.0106.0
CLOUDY4815.213.514.311.312.810.711.611.311.411.111.414.0148.6
PRMEAN STATION PRESSURE(IN)2929.6429.6129.5729.5429.5429.5529.5729.6029.6229.6529.6629.6729.60
MEAN SEA-LEVEL PRES. (IN)1830.1330.1230.0530.0030.0130.0030.0430.0430.0730.1230.1530.1730.08
WINDSMEAN SPEED (MPH)478.18.49.18.77.56.96.66.26.66.57.07.47.4
PREVAIL. DIR (TENS OF DEGS)3223232222232223220404232323
MAXIMUM 2-MINUTE:
SPEED (MPH)538454633333037364023324046
DIR. (TENS OF DEGS)28232423271606240322232224
YEAR OF OCCURRENCE199919971999200020012000199720011999200119992000MAR 1999
MAXIMUM 5-SECOND:
SPEED (MPH)570646145444352436132384970
DIR. (TENS OF DEGS)24232330282205032525232024
YEAR OF OCCURRENCE199919971999200020011998199719981998200119992000JAN 1999
PRECIPITATIONNORMAL (IN)303.483.693.772.593.923.684.014.023.192.862.983.2441.43
MAXIMUM MONTHLY (IN)577.526.427.786.107.679.3810.2712.1821.799.108.226.6521.79
YEAR OF OCCURRENCE195419891983197819741973199119861999199519481983SEP 1999
MINIMUM MONTHLY (IN)570.870.691.030.230.580.330.800.810.230.440.500.250.23
YEAR OF OCCURRENCE198119911985197619991993195319501985200020011965SEP 1985
MAXIMUM IN 24 HOURS (IN)573.113.223.704.044.403.444.275.205.414.244.703.185.41
YEAR OF OCCURRENCE198419731983197819571967199750201999199519631958SEP 1999
NORMAL NO. DAYS WITH:
PRECIPITATION 0.01309.89.410.18.710.59.110.79.87.06.67.89.3108.8
PRECIPITATION 1.00301.01.00.70.40.91.10.91.30.90.90.60.610.3
SNOWFALLNORMAL (IN)302.43.21.50.10.00.00.00.00.00.00.20.57.9
MAXIMUM MONTHLY (IN)5725.817.214.01.8TTT0.00.00.02.610.625.8
YEAR OF OCCURRENCE200019791960198319961996199319751958JAN 2000
MAXIMUM IN 24 HOURS (IN)5717.910.49.31.8TTT0.00.00.02.69.117.9
YEAR OF OCCURRENCE200019791969198319951996199319751958JAN 2000
MAXIMUM SNOW DEPTH (IN)5320101100000002920
YEAR OF OCCURRENCE20001979198020001958JAN 2000
NORMAL NO. DAYS WITH:
SNOWFALL 1.0300.90.80.40.*0.00.00.00.00.00.00.10.22.4
PRECIPITATION (inches) 2001 RALEIGH, NC (RDU)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
19721.974.132.501.925.344.166.804.175.803.965.985.0151.74
19732.675.504.064.403.999.383.124.601.130.600.616.3846.44
19744.392.873.341.327.674.021.564.823.711.231.794.0240.74
19756.092.856.261.643.841.666.742.115.771.234.604.0446.83
19763.071.543.170.234.742.551.001.525.993.971.894.0433.71
19772.822.135.631.893.940.840.894.123.865.062.223.7037.10
19787.031.434.406.104.204.063.631.861.371.464.173.2642.97
19795.715.552.692.634.713.274.841.666.761.884.730.9445.37
19804.391.915.871.972.334.892.111.873.762.252.871.4235.64
19810.873.022.351.034.280.555.695.342.704.640.954.9636.38
19823.434.973.023.334.208.393.341.831.553.932.344.0244.35
19831.796.007.783.545.893.091.101.812.133.593.866.6547.23
19844.935.655.404.455.433.089.201.132.310.731.642.3246.27
19854.834.441.030.643.952.876.283.730.231.757.610.8138.17
19861.881.653.061.012.981.924.3212.180.951.282.772.9536.95
19876.535.522.884.681.192.111.785.805.481.711.393.0242.09
19883.152.421.763.562.852.882.693.404.905.673.341.0437.66
19891.356.425.404.913.887.305.465.083.963.443.943.0154.15
19903.073.825.022.196.971.032.222.650.305.691.513.0837.55
19914.120.694.591.042.892.0510.271.873.161.400.732.6535.46
19923.802.232.951.932.605.123.457.632.223.795.022.4443.18
19934.502.226.134.843.320.332.111.773.502.952.663.7238.05
19943.552.975.910.862.852.204.674.201.994.621.321.2736.41
19954.504.522.491.323.917.753.292.702.469.104.671.8848.59
19964.242.943.393.983.263.286.983.7216.653.484.332.8959.14
19973.132.833.414.752.213.836.511.013.073.264.052.7540.81
19987.495.797.363.123.793.454.844.663.552.792.403.4452.68
19995.771.963.693.530.581.163.003.2021.792.451.202.3150.64
20006.272.201.764.661.232.506.196.643.82T2.561.5139.34
20011.302.347.111.723.534.544.134.880.861.860.502.0134.78
POR=115 YRS3.533.633.813.203.814.035.064.853.772.892.613.1744.36
AVERAGE TEMPERATURE (F) 2001 RALEIGH, NC (RDU)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
197244.740.049.558.064.369.977.175.670.457.448.146.258.4
197339.340.054.857.964.575.176.576.673.262.254.642.559.8
197449.342.954.460.267.471.876.576.069.056.548.743.259.7
197543.843.747.155.868.273.775.678.371.162.253.542.059.6
197637.650.156.260.766.874.778.675.469.755.742.537.158.8
197726.639.353.362.668.473.380.678.172.856.451.839.958.6
197835.333.148.259.266.075.878.079.973.759.555.144.959.1
197939.136.552.259.766.869.875.477.271.259.952.043.458.6
198040.636.546.562.069.875.078.979.674.958.749.140.759.4
198133.443.946.261.764.078.980.874.668.357.250.739.758.3
198235.545.551.757.471.074.779.176.570.560.651.947.560.2
198338.140.750.755.165.472.579.179.170.760.450.939.558.5
198436.345.747.255.965.575.574.976.667.566.347.149.759.0
198534.041.952.762.067.373.976.875.269.763.758.439.459.6
198638.544.551.761.267.478.481.775.672.363.052.942.660.8
198738.340.449.256.969.376.381.279.273.054.652.844.559.6
198834.741.950.657.866.072.479.080.370.354.452.042.458.5
198944.842.950.758.065.077.078.176.271.761.351.434.659.3
199048.051.054.960.367.475.280.078.072.264.154.248.162.8
199141.946.854.362.372.375.880.677.871.661.150.047.061.8
199243.446.250.559.263.272.080.474.171.558.151.942.559.4
199343.340.947.956.969.076.182.578.273.759.651.840.360.0
199436.944.252.263.664.277.079.676.069.159.354.047.960.3
199542.941.052.761.068.573.880.480.670.563.447.139.560.1
199638.342.545.358.467.776.478.675.270.361.045.745.858.8
199741.346.754.655.263.971.579.576.670.959.647.340.959.0
199844.746.150.258.869.277.379.577.874.661.152.046.661.5
199945.745.747.561.566.874.581.380.069.158.654.443.960.8
200038.445.853.457.670.077.277.076.169.460.248.035.559.1
200141.647.249.160.868.076.976.279.669.059.455.847.660.9
POR=115 YRS41.142.950.459.367.975.277.776.471.660.750.842.759.7

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.

HEATING DEGREE DAYS (base 65 F) 2001 RALEIGH, NC (RDU)
YEARJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNTOTAL
1972-730092385045767906923342318803462
1973-740021263126904816143461874802806
1974-7500442685016686515895532933403601
1975-7600171173517058434263001945263011
1976-77007302668857118371535813249144285
1977-780042834117689148835141968304056
1978-790071842926277937923981834383327
1979-8000131963946617538205641303303564
1980-8100162254777479735835791499903848
1981-8204312534257769075384112441503604
1982-8300141823925428286754383057973462
1983-8400591804177848825535452838353791
1984-850063425304689546443951464243288
1985-860036962077898125694151575903140
1986-87011121493706878206814842482903491
1987-8800131936263193266544422862223666
1988-8900833638669561962345925710203485
1989-9003301674049345183903571863703026
1990-9100181243235207095013541531802720
1991-92002415645156265953744622611433178
1992-9300292243906916666705242441503453
1993-94001919840575886357639411310103427
1994-950081903265276796653801653602976
1995-9600181235327878196466012277223827
1996-9700914256959072951032630097453317
1997-9800142235247426245254752072173362
1998-990071463835735935335361603622969
1999-0020292163146468185483652352403197
2000-0100401815119107184924902003603578
2001-0050211287532
COOLING DEGREE DAYS (base 65 F) 2001 RALEIGH, NC (RDU)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
197200537361703823361776621157
19730024268131036336525448701478
197400255113021036334716992101325
197500322141269337421209381201452
197603317111630442833015719001459
197702468162272490414245251901701
197800230120330412468275213101671
197900628105159332384205461001275
19800004519030644146032138601807
1981002567542549730913919001522
19820032420829944336318353571588
1983000169723844144723942001520
19840001610832431136614390001358
1985032065121277373323181641401441
198600751142408526349237961501831
1987000111703475084472500201735
1988035179824943848217214301481
1989011235411036741235923759401636
1990034951117312472410239102451764
1991002878253333493403230409131880
1992003586521848728522815301362
199300012147338550417286341701801
1994006788636746235013921311513
19953035315427048649019181301734
19960003516435242732417626001504
19971314116824945136819964001428
1998302329158382457401302320121799
19993006410029251347416124001631
20000091918537438035117638801540
200100383137364356461176461721645
SNOWFALL (inches) 2001 RALEIGH, NC (RDU)
YEARJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNTOTAL
1972-730.00.00.00.0T0.06.44.50.40.00.00.011.3
1973-740.00.00.00.00.02.80.0T2.90.00.00.05.7
1974-750.00.00.00.00.0TTT0.60.00.00.00.6
1975-760.00.00.00.02.6T0.4T0.00.00.00.03.0
1976-770.00.00.00.0TT2.11.50.00.00.00.03.6
1977-780.00.00.00.0TTT9.01.60.00.00.010.6
1978-790.00.00.00.00.00.00.417.2T0.00.00.017.6
1979-800.00.00.00.00.00.02.25.011.10.00.00.018.3
1980-810.00.00.00.00.03.12.60.0T0.00.00.05.7
1981-820.00.00.00.00.0T6.00.60.00.00.00.06.6
1982-830.00.00.00.00.0TT2.77.31.80.00.011.8
1983-840.00.00.00.00.00.0T6.9T0.00.00.06.9
1984-850.00.00.00.00.00.04.1T0.00.00.00.04.1
1985-860.00.00.00.00.0TT0.9T0.00.00.00.9
1986-870.00.00.00.0T0.00.610.2TT0.00.010.8
1987-880.00.00.00.00.60.07.3T0.00.00.00.07.9
1988-890.00.00.00.00.00.10.011.10.50.30.00.012.0
1989-900.00.00.00.00.02.70.0TT0.00.00.02.7
1990-910.00.00.00.00.0TTTT0.00.00.0T
1991-920.00.00.00.0T0.0TT0.00.00.00.0T
1992-930.00.00.00.00.0TT1.60.90.00.00.02.5
1993-94T0.00.00.00.03.1T1.10.20.00.00.04.4
1994-950.00.00.00.00.00.00.81.4T0.0T0.02.2
1995-960.00.00.00.0TT5.68.10.90.0TT14.6
1996-970.4T0.00.0TT
1997-980.00.00.00.00.00.42.00.0T0.00.0T2.4
1998-990.00.00.00.00.0TTTT0.00.00.0T
1999-000.00.00.00.00.0T25.80.00.00.00.0T25.8
2000-010.00.00.00.02.20.1T0.3TTT0.02.6
2001-0.00.00.00.00.00.0
POR=56 YRST0.00.00.00.10.82.62.51.30.0TT7.3

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