Office of the New Jersey State Climatologist
Department of Geography
54 Joyce Kilmer Avenue
Piscataway, NJ 08854-8054
Phone 1: 848-445-4741
Phone 2: 848-445-3076
Temperature differences between the northern and southern parts of the state are greatest in winter and least in summer. Nearly every weather station has registered readings of 100 F or higher at some time, and all have records of zero or below.
In the northern highland area, the average date of last freeze (32 F) in spring is about May 2nd, and that of the first freeze in fall is October 12th. On the seacoast corresponding dates are April 6th and November 9th, while in the central and southern interior the dates are April 23rd and October 19th. Freeze-free days in the northern highlands average 163, with 217 along the seacoast and 179 in the central and southern interior.
Northern New Jersey is near enough to the paths of the storms which cross the Great Lakes region and down the St. Lawrence Valley to receive part of its precipitation from that source. However, the heaviest general rains are produced by coastal storms of tropical origin. The centers of these storms usually pass some distance offshore, with heaviest rainfall and strongest wind near the coast. On several occasions tropical storms have moved inland along the south Atlantic coast, and then moved northward either through or to the west of New Jersey.
The average annual precipitation ranges from about 40 inches along the southeast coast to 51 inches in north-central parts of the state. In other sections the annual averages are mostly between 43 and 47 inches. Rainfall is well distributed during the warm months. Heavy 24-hour falls of 7 or 8 inches are occasionally recorded.
Brief periods of drought during the growing season are not uncommon, but prolonged droughts are relatively rare, occurring on the average once in 15 years. Flooding in New Jersey is usually caused by heavy general rains, at times associated with storms of tropical origin. Local flooding results from ice gorging.
The season during which measurable quantities of snow are like to fall extends from about October 15th to April 20th in the Highlands, and from about November 15th to March 15th in the vicinity of Cape May. Average seasonal amounts range from about 13 inches at Cape May to nearly 50 inches in the Highlands. Snowfalls of 10 or more inches in a single storm are occasional occurrences.
The number of days a month with measurable precipitation averages 8 for each of the fall months, September, October and November, and 9 to 12 for the other months of the year; the average yearly number is 120. Midday relative humidity averages 68 percent along the seacoast and 57 percent or less at inland locations.
Normally, sunshine varies from slightly over one-half of the possible amount in the northern counties to about 60 percent in the south. The prevailing wind is from the northwest from October to April, inclusive, and from the southwest for the other months of the year.
Tornadoes average less than one per year and most areas receive from 25 to 30 thunderstorms each year.
The invigorating climate of New Jersey, with marked changes in weather, generally neither extreme nor severe, provides an excellent setting for industrial and commercial interests, as evidences by the concentration of population in the state.
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