THE CLIMATOLOGY OF BERGENFIELD, NEW JERSEY

Based on records taken from 1983 to the present.

GEOGRAPHY

Bergenfield, located in Bergen County, New Jersey, has a total area of 2.9 square miles ( 7.5 km² ) and population of 26,764 ( est. 2010 ). The borough is typical of the suburban communities found in northeastern New Jersey. Virtually all its building lots are occupied by one and two-family homes. A few light industries are scattered throughout the town. Main Street, bisecting the borough from north to south is lined with commercial establishments. Bergenfield can be described as built-up suburban. The town's official elevation, taken at the Post Office building, is 66ft. I live about 3/4 of a mile to the west of the P.O. at an elevation of 110ft. There are no substantial variations in topography within Bergenfield. The Ramapo Mountains, a chain of the Appalachian Mountains running through northeastern New Jersey and southeastern New York, lie to the north and northwest about 25 miles from Bergenfield. Elevations here can reach 900 to 1200ft. However, the Ramapo Mountains probably have a minimal impact on our weather and climate.

TEMPERATURE

My weather site is located about 10 miles W/NW of New York City's official weather site in Central Park. Weather conditions here in Bergenfield are generally similar to those in Central Park. However, as described in the Urban Heat Island section of this website, temperature comparisons between N.Y.C. and Bergenfield can show considerable variation given the right weather conditions. January's average temperature is slightly below freezing. A typical day would see a maximum near 40ºF. and a minimum of 24ºF. Most winters will see some 'ice days' with temperatures remaining below the freezing point all day long. Mild spells with maximums above 50ºF. and sometimes 60ºF. occur every winter. March is a transitional month. With the vernal equinox occuring on the 21st, the sun makes considerable progress in its journey north. The days lengthen noticeably and any cold spells that do visit the area tend to be short-lived. Vegetation springs to life in April. Daily highs average in the low 60ºF´s. Most years will see some morning frosts, but the month will usually end with a few days registering high temperatures above 70ºF. Summer in Bergenfield will bring high temperatures reaching the middle and upper 80ºF´s. Spells of uncomfortable humidity are common. September holds the promise of relief from summer´s sultry weather. Temperatures above 80ºF become less frequent and some mornings will see low temperatures falling below 50ºF. With the autumnal equinox arriving towards the end of the month, the number of daylight hours show a marked decline. October brings a rapid fall in average temperatures. A few days of morning frost usually occur by the end of the month and maximum temperatures above 80ºF. become infrequent. November brings mild afternoon temperatures in the 50ºF´s following crisp A.M. readings in the 30ºF´s. This is actually my favorite time of the year. Summer's heat and humidity are well behind us with the anticipation of some exciting winter weather looming just over the horizon. Temperatures in December average about 10ºF below those in November. The total hours of sunlight reaches an annual minimum on December 21st as the winter solstice arrives.

Temperatures in Bergenfield can vary considerably from year to year. The lowest average monthly temperature, 22.1ºF., recorded in February 2015, is comparable to what could be expected along the coast of Maine. The warmest January, 39.8ºF., is similar to winter temperatures in southeast coastal Maryland. Summer months can be quite sultry with spells of unbearable heat and humidity. A few heat waves with maximum temperatures in the 90ºF.'s can be expected every year. July 2010 saw temperatures averaging 80.1ºF. You would have to travel in South Carolina or Georgia to find similar conditions in an average year. The period from March through July 2010 was particularly warm. Each month set a new record average temperature.

On 6 July 2010 I recorded an all-time high temperature of 105ºF. The temperature in my backyard fell to -7ºF. on 22 January 1984. In Central Park, the minimum temperature was 10ºF.; a full 17ºF. higher. This was a good example of the urban heat island effect at its strongest. Clear skies, no wind and a snow cover of 7" made for optimal radiational heat loss at my weather site. Can the temperature fall below 0ºF. in Bergenfield and the New York City metro region without the presence of a snowcover? This is the sort of debate we often have at meetings of The North Jersey Weather Observers. Well, it happened on January 16th, 2004 for the first time since 1983 in Bergenfield. An examination of the record shows that low temperatures below 10ºF. can be expected at least once almost every winter. Since 1983, the average date of last frost in spring is April 15th. The average date of the first frost in fall is October 25th. My latest spring frost occured on May 14th, 1996. This was the only time I have ever recorded a low of 32ºF. in May. Temperatures above 70ºF. have been noted in each of the winter months. Summer-like warmth, with maximum's above 80ºF. has occured in each of the months from March through November.

PRECIPITATION

Rainfall is distributed fairly evenly throughout the year, from an average maximum of 4.39" in July to a minimum of 3.02" in February. The February total seems to be somewhat anomalous. Even though February is 2 or 3 days shorter than the other months, its precipitation total is unexpectedly low, especially considering that it is the snowiest month of the year. I'm not sure how to explain this. Rainfall sums have varied from a high of 16.17" in August of 2011 to a low of 0.37" in July of 1999. The greatest single-day total was 9.00" on the 15th of September 1999 as Tropical Storm Floyd passed through the region. The storm's two day total ( 15th and 16th ) was 9.77" There was serious street flooding throughout the region. Several inches of water seeped into my finished basement, ruining the carpeting and damaging personal items. It took several months to completely dry out. August 2011 brought several heavy rainfall events culminating with Tropical Storm Irene on the 27th and 28th. Another noteworthy rainfall event occured in October of 2005. The second week of the month saw 11.39" precipitation fall in several heavy showers with little time for the ground to dry out. The nearby Hackensack River overflowed its banks and reached historic flood heights. There have been occasional short term droughts but rainfall in the Bergenfield region can usually be depended upon for most gardening activities.

SNOWFALL

Snowfall totals average a little more than two feet each year, however, this long-term average is deceptive. The variation from year to year is enormous. I measured a record 79.9" during the 1995/1996 snow season. On the other hand, only 5.4" fell in 2001/2002. A number of pre-conditions must be met for heavy snowfall in Bergenfield. If a disturbance passes to the west of us, we will be in the storm's warm sector, characterized by onshore winds from the east and southeast. No matter how cold the air is at the storm's onset, mild Atlantic air will eventually be drawn into our region and change the snow into liquid precipitation. The ocean waters offshore are always above freezing, even during the coldest winters. The ideal air trajectory for snow-lovers will be from the north to northeast. This occurs when storms move up the coast to our east. Our heaviest falls result when a coastal disturbance moves slowly up the Atlantic Coast, about 50 - 75 miles offshore. The record single storm total in Bergenfield was the 20.0" that fell on January 7 - 8th in 1996. This storm took place in a winter season that was quite remarkable. Every month from December through March saw above normal snowfall. Bergenfield usually receives more snowfall than New York City when precipitation events occur with air temperatures close to or just below freezing. Ground surface temperatures here tend to be colder. It is not uncommon for a few inches of snow to accumulate on lawns in Bergenfield while the ground remains barren and wet in the city. Heavy snow is rare in April but in 2018 6.7" fell on the 2nd. Conditions became severe enough that snowplows were called out to clear the streets.

Our Local Urban Heat Island

The Urban Heat Island effect has been widely discussed and documented. A number of factors are responsible for this phenomena.

1. The concrete and asphalt commonly found in urban areas have different thermal properties compared to the more widespread vegetation found in nearby suburban regions. They absorb and store heat during the day and release it slowly during the nightime hours. This results in relatively elevated overnight temperatures in the city.

2. Urban geometry also causes what is known as the ‘Canyon Effect’. Tall buildings provide multiple faces that serve to reflect and absorb heat energy. Tall buildings can also block the free flow of air which will inhibit cooling by convection.

3. Human activity, waste heat from autos, buses and trucks and air conditioning all contribute a small but significant amount of heat.

4. The lack of vegetation in built-up urban areas inhibits cooling by evapotranspiration.

A comparison of temperature records from Bergenfield, New Jersey and Central Park in New York City provide another Heat Island example. Bergenfield is well within the New York City metropolitan area, only 10 miles from Central Park. However, the daily maximum and minimum temperature profiles of the two sites show marked differences.

Difference Between Max and Min Temperatures ( Bergenfield vs Central Park, N.Y.C. )

The table above is based on temperature data from 1991 - 2020. A close inspection of this record shows some interesting effects. During the winter months the maximum temperatures recorded in Central Park and Bergenfield are quite similar. However as summer approaches, it becomes hotter in Bergenfield. The July maximum in Bergenfield averages a full 2.0°F. higher than Central Park. Notice how this temperature difference rises and falls during the course of a year. I suspect that, to some extent, the cooler high temperatures found in the city during the summer are a result of onshore sea breezes that frequently develop during the warm months of the year. The city is close to the ocean and surrounded by water on all sides. Bergenfield is just far enough inland to be out of reach from these cooling breezes.

Bergenfield has colder morning temperatures throughout the year. The difference is smallest during the summer months and greatest during the fall. This temperature anomaly during the autumn months is not what I anticipated. I had assumed that the longer winter nighttime hours would provide more time for temperature contrasts between my site and Central Park to develop. Maybe there is an increase in average cloudiness during the winter months that would inhibit overnight cooling. Also, high pressure systems that stall over the region and provide ideal radiational cooling conditions with clear skies with little or no wind may be more frequent during the fall. These periods are known as "Indian Summer" with brisk morning temperatures and mild afternoons.

During the winter, fall and spring months, minimum temperatures are frequently 5 to 10ºF. cooler in Bergenfield. With the right conditions, this thermal deficit can be extreme. The temperature in my backyard fell to -7ºF. on 22 January 1984. In Central Park, the minimum temperature was 10ºF.; a full 17ºF. higher. This was a good example the urban heat island effect at its strongest. Clear skies, no wind and a snow cover of 7" made for optimal radiational cooling.

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