South Plainfield (NJ) Temperature by Month

South Plainfield in New Jersey, United States of America sees significant seasonal temperature differences, with daytime highs between 5°C (41°F) in January and 31°C (88°F) in July, averaging 18°C (64°F) annually. Explore the full monthly breakdown below.

With significant temperature fluctuations, South Plainfield enjoys distinct seasons year-round. Nighttime lows range from 19°C (66°F) in July to -5°C (23°F) in January.

The chart below illustrates the average maximum day and minimum night temperatures in South Plainfield by month:

Low temperatures are most often recorded between 4 AM and 6 AM, while highs typically occur around 3 PM. July, the city's warmest month, sees 271 hours of sunshine.

The chart below shows the average temperature throughout the year:

South Plainfield's average annual maximum temperature is 18°C (64°F). To put that in context, here's how it compares to a few well-known destinations:

Barcelona, Spain has an annual average of around 21°C (70°F), with warm summers and mild, fairly short winters.

Glasgow, Scotland averages 13°C (55°F) a year, mild but often grey, with cold winters and rarely hot summers.

San Francisco, USA averages 19°C (66°F) annually, but with little seasonal variation, summers are often cool and foggy, winters mild.

Melbourne, Australia averages 20°C (68°F) annually, known for unpredictable weather, with four seasons sometimes happening in one day.

Temperature alone doesn't tell the whole story, humidity plays a big role in how warm or cold it actually feels. High humidity in summer makes the heat feel more intense, particularly once temperatures climb above 25°C. In winter, the same humidity can make cold air feel sharper than the thermometer suggests.

In the cooler months, when temperatures drop below 10°C, high humidity makes the cold feel more cutting than it would in dry conditions.

In South Plainfield, January is the coolest month, with average highs of 5°C (41°F) and humidity around 61%, considered high. In July, the warmest month, temperatures average 31°C (88°F) with 64% humidity, conditions that feel high. For a full picture, see our humidity page.

Climate temperature data is typically calculated as a 30-year average. This smooths out year-to-year variability and gives a more reliable picture of what a place is actually like, rather than what happened in any single unusual year.

The readings come from a range of sources, land-based weather stations, ocean buoys, ships, and satellites. That data is collected by weather services around the world, then pooled, quality-checked, and averaged to produce the climate records you see here.

Seasonal temperature shifts influence more than just how warm it feels, they also drive changes in rainfall, cloud cover, and wind patterns throughout the year.

Warmer air holds more moisture, which tends to mean heavier or more frequent rain during the warmer months. When temperatures drop in winter, any precipitation that does fall is more likely to come as snow or sleet, though in South Plainfield this rarely lasts long on the ground.

For more on South Plainfield's weather, including monthly rainfall, sunshine hours, and humidity, visit our South Plainfield climate page.