Mountainside is a city of approximately 6,900 people in New Jersey, United States. Located in the Eastern Time Zone at 40.7°N latitude.
In 2025, Mountainside recorded an average annual temperature of 54°F — about 1.6°F below the 30-year normal of 56°F. The hottest day reached 103°F in June; the coldest was 3°F in January. Total precipitation was 42 inches (drier than usual). Snowfall totaled 8 inches, below the 32-inch average. The wettest month was May.
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