INTRODUCTION
This Local Climate Report is excerpted from the Cranford Environmental Commission’s Natural
Resource Inventory. The original Natural Resource Inventory was published in December of 1993.
The updated Natural Resource Inventory was published in December of 2003. The original text of the
1993 Natural Resource Inventory appears below with the 2003 updates and additions in red italics.
The data tables presented show a ten year difference in data and may be used as a micro analysis of
weather changes over the ten year period.
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VIII. CLIMATIC CONDITIONS 1,6(2001 update)
The climate of Cranford is typical of the Middle Atlantic seaboard. It may be classified as a
modified continental type climate because the prevailing westerly winds are altered by air masses
originating over the ocean and moving on shore. The moderating effect of the ocean is felt during both
the winter and summer seasons. During this period, coastal storms accompanied by easterly winds can
produce heavy precipitation, although moderate rainfall more commonly occurs.
A major regional weather characteristic is instability caused by high pressure air masses which
move in from Canada and conflict with low pressure air masses moving from the south. This results in
periodic cool spells during the summer and periods of relatively warm, spring-like weather in winter.
The storms experienced in Cranford are classified in four general groups: thunderstorms, cyclonic
or transcontinental storms, extratropical storms, and hurricanes.
Thunderstorms normally occur with the most frequency in the months of July and August. They
are usually of brief duration and are limited in area. These storms, when intense, can cause local flooding
in areas of the Township where storm sewers are not of sufficient size to accommodate the resulting surge
flows. The general path of these storms is in a northeasterly direction.
During autumn, winter and spring, cyclonic storms predominate. These storms are due to
movements of transcontinental air masses with attendant high and low pressure areas. Intense storms of
this type are potent flood producers over large areas because of their wide range.
These storms can cluster together and last for many days, depositing four, five or more inches of
precipitation over their duration. The duration of these storms, coupled with the continuous rainfall, can
cause the Rahway River to rise above the storm sewer stream encroachment near the end of the storm
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event. This slows storm sewer drainage and causes street flooding as a result. In extreme cases, the
Rahway River rises so high that river water will enter the street, causing flooding that will linger until the
river recedes below the storm sewer encroachment elevation.
Extratropical storms are due to the rapidly convective circulation that results when tropical marine
air masses are lifted suddenly on contact with hills and mountains. They usually cause heavy rain in the
summer and autumn seasons.
A hurricane is defined as a spiraling tropical low pressure system, formed by the release of latent
heat from ocean water condensation, with sustained wind speeds of 74 m.p.h. or greater. Because of its
size and duration, a fully developed hurricane is the most destructive of storms. Hurricanes only form in
certain areas of the earth at specific times of the year. Those affecting the United States form in the
western Atlantic Ocean, near the Cape Verde Islands, and in the western Caribbean Sea. Hurricane
season there runs from June 1 to November 30.
METEOROLOGICAL DATA
There are no official meteorological stations located in Cranford. 2The Cranford station
(located at 40'North Latitude, 74 18' West Longitude) on the grounds of Union County College
is a National Weather Service Cooperative Observing Station. The station’s personnel manually take
and manually record singular daily temperature and precipitation data only. It has been in existence
for about 30 year; thus it does not have a long record of observations useful in assessing the
magnitude of recent events. Observations from Newark are rather adequate surrogates for Cranford,
and as noted above they are the only local observations for variables other than precipitation and
temperature. All variables are automatically recorded instantaneously or hourly depending upon the
parameter, and are electronically entered into the climatic database. The Newark weather station is
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located at Newark International Airport, approximately 10 miles east northeast of the Township
(located at 40 42' North Latitude, 74 10' West Longitude). This station measures and keeps records
on various weather-related phenomena such as temperature, barometric pressure, relative humidity,
wind and cloud cover. Summaries of each are presented below:
1.
Temperature
In the last ten year period, the mean annual temperature at the Newark station increased from 54.2
degrees to 54.8 degrees Fahrenheit. The coldest month is January, with an average temperature of 30.6
degrees, a decrease from 31.5 degrees Fahrenheit in the last ten years. July is the hottest month of the
year, with an average temperature of 77.8 degrees increased from 76.8 degrees Fahrenheit in the last ten
years (see Table 5a). Temperature readings of above 90 degrees and below 0 degrees Fahrenheit are not
unusual occurrences. The record high of 105 degrees Fahrenheit was first set in July of 1966 and equaled
during July of 1993. The record low temperature of -8 degrees Fahrenheit was set in January of 1985.
The average annual heating degree days decreased in past ten years from 4,972 to 4,888 and ranges from
5,577 to 4,086. The average annual cooling degree days increased over the past ten year period from
1,091 to 1,201 and ranges from 1,490 to 982 (see Table 5b).
2.
Barometric Pressure
Barometric pressure averages 1,016.1 millibars annually, with monthly averages ranging from
1,013.7 to 1,018.1 millibars (see Table 6a).
3.
Relative Humidity
Depending upon the time of day, the average annual relative humidity ranges between 53 and 73
percent (see Table 6b).
4.
Precipitation
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An average of 42.34 inches of rain falls annually at the Newark station. Normally, this rainfall is
distributed evenly throughout the year, with average monthly rainfall ranging from 2.94 to 4.3 inches each
month. 2Neither Hurricane Floyd of September 16, 1999, nor the two major preceding storms of July 25,
1997 and October 20, 1996 altered the record for the maximum monthly rainfall which stood at 11.84
inches in August of 1955 and now stands at 22.48 inches.
The minimum monthly rainfall was recorded in June of 1949 at 0.07 inches. The maximum
rainfall that occurred in a 24-hour period occurred in August of 1971 and amounted to 7.84 inches.
2
Neither Hurricane Floyd of September 16, 1999, nor the two major preceding storms of July 25, 1997
and October 20, 1996 altered the maximum 24-hour period rainfall record.
Precipitation data is summarized in Table 7a.
The abundant precipitation in the Cranford area has made groundwater recharge adequate and has
helped the area's vegetative ground cover and tree population to temporarily retain water and minimize
erosion.
Precipitation during the winter months often falls in the form of snow (see Table 7b). The
average annual snowfall in Cranford is approximately 27.7 inches. The monthly maximum of snow for
the area stood at 29.1 inches, recorded in December of 1947, a portion of this amount (26.0 inches) was
the result of a record 24-hour snowfall. 2Recently, however, a new record was set when Newark Airport
recorded 33.4 inches of snow in February of 1994. Newark Airport also recorded 31.6 inches of snow in
January of 1996, 27.8 inches of which were attributable to the blizzard that occurred on January 7 and 8,
1996. Snow can be expected to fall from October to May. The average monthly snowfall at the Newark
station is shown below in Table 4.
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TABLE 44, 8
AVERAGE MONTHLY SNOWFALL, ICE PELLETS, AND SLEET – (inches)
Month
September
October
November
December
January
February
March
April
May
Annual
Snowfall - (inches)
Trace
Trace
0.5 0.6
5.6 5.5
7.7
7.9 8.3
4.5 4.9
0.7
Trace
27.7
Rainfall of 0.01 inches or more occurs on an average of 121.7 days annually and ranges from 11.3
to 15.4 days per month. Snowfall of 1.0 inch or more occurs on an average of 7.1 days annually and
ranges from 0.0 to 2.2 days per month.
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TABLE 5a
Temperature Degrees Fahrenheit4
Normal7
Daily Maximum
Normal7
Daily Minimum
January
38.2 37.7
February
Monthly
Average7
Record High8
Record
Low8
24.2 23.4
31.3 30.6
74
-8
40.3 40.5
25.3 25.4
32.8 33.0
76
-7
March
49.1 50.8
33.3 33.4
41.2 42.1
89
6
April
61.3 61.9
42.9 42.7
52.1 52.3
94
16
May
71.6 72.4
53.0 53.2
62.3 62.8
98 99
33
June
80.6 82.3
62.4 62.8
71.5 72.6
102
43
July
85.6 87.0
67.9 68.6
76.8 77.8
105
52
August
84.0 85.4
67.0 67.4
75.5 76.4
103
45
September
76.9 77.6
59.4 59.9
68.2 68.8
105
35
October
66.0 66.7
48.3 48.2
57.2 57.5
92
28
November
54.0 55.4
39.0 39.2
46.5 47.3
85
15
December
42.3 42.9
28.6 29.1
35.5 36.0
72 76
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Annual
62.5 63.4
45.9 46.1
54.2 54.8
105
-8
Month
TABLE 5b
Normal Degree Days4, 7
Month
Heating
Cooling
1045 1066
0
February
902 897
0
March
738 710
0
April
387 381
0
May
140 127
56
January
59
June
0
199 232
July
0
366 397
August
0
326 353
September
36 26
132 140
October
254 252
12
November
555 531
0
December
915 899
0
Annual
4972 4888
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20
1091 1201
TABLE 6a
Monthly Normal Barometric Pressure
Month
Barometric Pressure
(millibars)
January
1016.9
February
1016.9
March
1016.0
April
1013.7
May
1014.1
June
1014.0
July
1014.5
August
1015.9
September
1017.5
October
1018.1
November
1017.6
December
1018.1
Annual
1016.1
TABLE 6b4, 9
Monthly Normal Percent Relative Humidity
0100
Hr.
0700 Hr.
1300 Hr.
1900 Hr.
January
70
74 73
58 59
64
February
69
72
54
60
March
66
69 70
50 51
57
April
66
66
48
54
May
72
70
51
58
June
72
71
51 52
58
July
73
72
52
59
August
76
75 76
53
62
September
77
78
55
64
October
76
79
53
64
November
73
77 76
56
64
December
72
74
59 58
64
Annual
72
73
53
61
Month
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TABLE 7a4, 5, 8
Monthly Average of Normal, Maximum, and Minimum Precipitation (inches)
Month (days)
Normal
1
Maximum
1, 5, 11
Minimum
1, 5, 11
Daily Maximum
(11)
February (10)
March
(11)
April
(11)
May
(12)
June
(10)
July
(10)
August
(10)
September (9)
October (8)
November (10)
December (11)
3.13
10.10
0.45
3.59
3.05
4.94 6.82
1.22 0.69
2.45
4.15
11.14
1.10 0.72
2.83
3.57
11.14
0.90 0.7
3.73
3.59
10.22
0.52
4.22
2.94
6.40 11.51
0.07
2.31
3.85
9.98 19.09
0.89 0.84
3.63
4.30
11.84 22.48
0.50 0.27
7.84
3.66
10.28 17.66
0.95 0.14
5.27
3.09
8.20 13.84
0.21
3.04
3.59
11.53
0.51 0.35
7.22
3.42
9.47
0.27
2.77
(122)
42.34
11.84
0.07
7.84
January
Annual
TABLE 7b2
Monthly Maximum and Daily Maximum of Snow, Ice Pellets, and Hail (Inches)
Month
Maximum
Daily Maximum
2
January
27.4 (31.6 Jan 1996)
February
26.1 (33.4 Feb 1994) 2
20.0
March
26.0
17.6
April
13.8
12.8
May
Trace
Trace
June
0.0
0.0
July
0.0
0.0
August
0.0
0.0
September
0.0
0.0
October
0.3
0.3
November
5.7
5.7
December
29.1
26.0
Annual
29.1
26.0
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17.8 27.8 (two day storm)
1
5.
Wind
The normal prevailing wind direction is from the west to east for eleven months of the year.
January is the exception, when the prevailing winds are from the northeast. Average monthly wind
velocity ranges from 8.7 miles per hour (mph) to 11.9 mph, with an annual average of 10.2 mph. The
peak gust recorded at the Newark station was 83 mph. Average and peak wind data is presented in Table
9.
6.
Cloud Cover
The mean annual amount of cloud cover is 62 percent. There is no data for the amount of cloud
cover between sunset and sunrise. The following data in Table 8 is a list of daytime cloud cover only:
TABLE 8a
AVERAGE PERCENT DAYTIME CLOUD COVER
Average Cloud Cover – (percent)
Month
January
February
March
April
May
June
July
August
September
October
November
December
65
64
63
64
65
62
62
60
57
55
64
64
Annual
62
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TABLE 8b4,12
AVERAGE NUMBER OF CLOUDY DAYS
Month
January
February
March
April
May
June
July
August
September
October
November
December
Annual
Clear Days
Partly Cloudy Days
8
7
8
7
6
7
7
Cloudy Days
8
8
8
9
11
11
12
8
16
13
15
14
14
12
12
12
12
10
11
8
8
9
8
8
8
93
12
12
14
15
112
160
TABLE 91, 4, 10
Average and Peak Wind Data
Month
Normal Average Speed
(mph)
Normal Prevailing
Direction
Maximum Speed
(mph)
Direction
(degrees)
Peak Gust
(mph)
Direction
*
January
11.2
NE
52
300
53
W
February
11.5
NW
46
230
58
NW
March
11.9
NW
43 45
270 300
56
W
April
11.3 11.2
WNW
50
270
55
E
May
10.1 10.0
SW
50
320
58
NW
June
9.5
SW
58
260
83
W
July
8.8 8.9
SW
52
350
69
NW
August
8.7
SW
46
090
68
N
September
9.0
SW
51
050
67
W
October
9.4
SW
48
110
53
SW
November
10.2
SW
82
090
63
NW
December
10.8
SW
55
032
60
NW
Annual
10.2
SW
82
090
83
W
*
- fastest observed in one minute.
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Cranford has a wide variety of weather styles which contribute to the distinct seasonal differences
experienced by the Township.
These include rainfall, snowfall, thunderstorms, hailstorms and
windstorms and are generally neither extreme nor severe. Table 10 below presents a listing of the
average duration of the distinct weather types by month.
TABLE 10
Mean Number of Varying Weather Days
Month
Rainfall Snowfall Thunderstorms Heavy Fog
(a)
(b)
(c)
Clear
(d)
Partly Cloudy
(d)
Cloud
y
(d)
January
10.9
2.2
0.2
2.1
7.8
7.8
15.4
February
9.7
1.9
0.2
1.7
7.3
7.5
13.4
March
11.2
1.2
1.0
1.4
8.0
8.6
14.4
April
11.0
0.2
1.5
1.0
7.3
8.9
13.8
May
11.9
0.0
3.7
1.7
6.3
10.7
13.9
June
10.3
0.0
4.9
1.2
6.8
10.9
12.3
July
10.1
0.0
6.0
0.5
6.6
12.2
12.2
August
9.4
0.0
4.6
0.5
7.8
11.5
11.7
September
8.3
0.0
2.2
0.8
9.6
9.0
11.3
October
7.8
0.0
1.1
2.0
10.8
8.6
11.7
November
10.1
0.2
0.5
1.8
7.6
8.3
14.1
December
10.9
1.4
0.2
1.8
8.0
8.0
15.0
121.7
7.1
26.2
16.5
94.0
111.9
159.3
Annual
Notes:
a = 0.01 inches or more.
b = 1.0 inches or more of snow, ice pellets, and hail.
c = 0.25 mile or less visibility.
d = sunrise to sunset.
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New Jersey’s Weather2
New Jersey’s weather and climate offer something for everyone. In a month’s time one might observe
record high and low temperatures being broken, tornadoes touching down, severe thunderstorms
passing through, and a snowstorm blanketing the region. While rare, all occurred in November of
1989. A single year may bring a serious drought, an inundating flood, extreme heat, numbing cold, a
damaging hurricane, a stinging blizzard. All but the cold and snow were exhibited in 1999. A
relatively cool summer, sunny fall, manageable winter, and mild spring are also enjoyed from time to
time.
This weather and climate potpourri is a result of New Jersey’s middle latitude location. This
geographic positioning results in the state being influenced by wet, dry, hot, and cold air streams,
making for four relatively well defined seasons and leading to potential clashes between cold and
warmth, triggering occasional severe conditions.
This introduction will discuss the wettest time of the year, New Jersey drought frequency, long term
monthly means, and variability over time.
Cranford geographically lies at the southern portion of the northern land area as it boarders the
central land area. From a climatalogical standpoint, Cranford lies in the northern region and enjoys
the climate of the elevated region with the moderating effect from ocean on–shore air masses.
It is important to know how precipitation data is gathered. Since the late 19th century, trained
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observers at several dozen National Weather Service observing stations across the state have taken
daily observations of precipitation, snow, and temperature. National Weather Service professionals
operate some stations, but volunteers at Cooperative Observing Stations record most of the data.
Manual and electronic gauges are used to measure rain and melted snowfall, which, combined, equal
precipitation. The statewide values presented in this introduction are calculated as an average of all
of the stations operating at a given time; regional values are for northern and southern counties, with
a narrow strip of coastal counties comprising a separate region.
The data and figures discussed are from monthly and annual precipitation for the state and sub
regions from 1895 to present.
An excellent climatology of New Jersey’s annual precipitation regime is available for scrutiny
because of over a century of data on file. Between 1895 and 2000, the average annual precipitation
across New Jersey was 44.80 inches. From year to year this has varied by as much as plus or minus
35% of the mean, with as little as 29.36 inches in 1965 and as much as 59.98 inches in 1996. On
average there is an equitable distribution of precipitation throughout the year. The wettest month,
August with 4.59 inches is only 1.44 inches greater than the driest month, February with 3.15 inches.
Of course, many months vary considerably from the long term mean, witness the driest month on
record, 0.24 inches in June of 1949, and the wettest, 11.44 inches in August of 1955.
Regionally, the northern division is the wettest, followed by the southern, and then coastal divisions.
Annual precipitation from 1895 to 2000 averages 46.05 inches in the north, 44.33 in the south, and
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42.04 along the coast. Precipitation in the north is enhanced by atmospheric lifting provided by its
elevated terrain. The coast has less rain in the summer, as the stable, cooling influence of the ocean
results in fewer drenching thunderstorms.
The long-term annual mean is 2.3 inches less than the 1971-2000 mean of 47.19 inches. This clearly
indicates that, in addition to the marked year-to-year variability in precipitation, there are also
longer-term variations. On a decade basis, the last half of the 20th century included the 1st (1971-80),
2nd (1981-90), 3rd (1951-60), 4th (1991-2000), and 10th (1961-70) wettest decades of the century. With
the exception of the drought-filled 1960s, New Jersey has experienced a much wetter regime of late,
with approximately a 5 % increase in precipitation over the past century. The long-term increase in
precipitation is seen most strongly in the northern half of the state. This region experienced an
approximate 10% increase over the century, even with the dry decade of the 1960s.
New Jersey has its share of flooding events, be the flash floods or major river floods, as seen in
recent years, including the Sparta/Hopatcong event in August of 2000 and the Hurricane Floyd flood
of September 16, 1999. Human development, heavy rain, sometimes in combination with a rapidly
melting snow pack, are the major dictating factors. In contrast, a dearth of reduced winter
storminess, non existent tropical moisture, and meager thunderstorm rains can lead to protracted
periods of dry conditions or drought. The past two decades saw precipitation deficits in 1980-81,
1984-85, 1994-95, and 1998-99. However, these extended periods of below average precipitation
have not lasted for more than a year. None have come close to matching the drought that occurred in
the early and middle 1960s, the most severe drought of the 20th century, and perhaps for many
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centuries based on tree ring analysis, nor has any had the longevity of several other droughts earlier
in the 20th century.
It is impossible to predict whether the wet precipitation regime of the past four decades will persist
into the early decades of the 21st century, or whether the drier pattern of the first half of the 20th
century becomes reestablished. Nor can it be determined if the tendency for the reservoir-rich
northern part of New Jersey will continue to exhibit a greater increase in precipitation than the
remainder of the State. The protracted drought of the 1960s was a seemingly rare situation; so too
may be the conditions experienced in recent decades, with extended periods of below average
precipitation not lasting more than a year. Results of continued monitoring and research of New
Jersey’s precipitation regime will be useful in preparing for floods, droughts, and any hydrologic
changes in the 21st century.
Notes:
Updates are in red Italics. Updates are as of November 1, 2001
1
The Normals database report is updated on a 10 year basis. The decade ending 2000 will be added
to the database report which is due out by mid 2002 or later. That will span the period 1961 to 2000.
Because this NRI publication deadline is earlier, most of the data in this section of the NRI is from
the data report dated from 1961 to 1990.
2
Data, information, text, and analysis supplied by the New Jersey State Climatologist.
3
From the New Jersey State Climatological data.
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4
From the National Climatic Data Center – National Oceanographic and Atmospheric Agency and
the National Weather Service.
5
From Newark Weather Almanacs.
6
Data and substantive text changes and text additions are in red.
7
30 years of data.
8
59 years of data.
9
35 years of data.
10
52 years of data.
11
158 years of data.
12
53 years of data
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