Cumberland County Climate
Climatically speaking, Cumberland County is fortunate. Because of its southerly location, its many miles of frontage on the Delaware Bay, and its site as part of the southern New Jersey peninsula, the county has a relatively mild climate. The modifying influence of the Atlantic Ocean and the Gulf Stream, tempers the climate of the region and affords its inhabitants longer summers and milder winters than inland regions of similar latitude. In fact, the entire area of southern New Jersey is distinguished by its lack of extremes. While it has a four season climate, the large nearby bodies of water tend to retard the seasons. At times the high humidity renders the cold of fall and winter very penetrating and summer heat oppressive. An average annual temperature of 54° F. ranks the area high in the state. Mean seasonal temperatures within the county vary from 2° to 6° F., The lowest temperature recorded is 8° below zero (F.) and has occurred both in January and February. The highest temperature recorded is 104° F. and had occurred in both July and August . The average annual temperature ranges from about 56° Fahrenheit in the southern part of the county to about 52° F. in the north. Average monthly high temperature registered at Bridgeton reaches approximately 77° F. in July. The average low point is 17° F. and occurs in January.
There is some variation in the length of the growing season in different parts of the county, but the average length is 191 days in Bridgeton. This is considered a fairly long season which enables the farmers to make very early plantings in the spring, and to rely on crops maturing late in the fall. The average date of occurrence of last killing frost in spring is April 16; latest recorded, May 29. The average date of the first occurrence of killing frost in fall is October 24; latest, December 22.
From several standpoints, the precipitation aspects of our climate are of more concern than those of temperature. Cumberland County is well-watered by most standards, but it is still among the drier counties of New Jersey. Rainfall during an average year ranges from about 42" in the south to 45" in the north. A 44" average annual precipitation rate, however, ranks Cumberland fairly close to the general average for the state. In the wettest year on record, the county had an average precipitation of 61", 17" more than normal; during one of the driest years on record (1964), the county received only 32" of rainfall. Even in the driest year, however, there seems to be an ample supply of water below ground. In this sense, the county is fortunate that its source of water is underground aquifers rather than surface bodies, which are more affected by reduced rainfall. The monthly pattern of precipitation demonstrates the relative uniformity of precipitation throughout the year, with the slightly higher values occurring during the summer months.
There is a primary late summer maximum of precipitation and two secondary maxima, one in the fall and another in (early) spring. Precipitation data reflect the late summer maximum characteristic of the Atlantic Coast and are traceable to hurricanes and tropical storms. Some difference between July--August precipitation at different locations within the county may be attributed to summer thundershowers at interior locations as opposed to "cool" bayshore locations. The snowfalls are usually light, and the snow generally melts soon. Precipitation over the years, nevertheless, when compared with many parts of the United States, has normally been spread fairly evenly throughout the year. However, exceptionally sandy conditions coupled with several drought periods occurring during the growing season have led to local growers to rapidly expand irrigation facilities.
Prevailing wind directions in the county are generally form the north or northeast in the late fall, winter and spring months, and from the southeast, south, or southwest in the summer and early fall months. Normally, the amounts of time during which the sun shines equals 60% of the total possible in the county, which compares with the 50% in the northern New Jersey counties.