With a population of around 56,900, Diamond Bar sits in California, United States. The city operates in the Pacific Time Zone.
In 2025, Diamond Bar recorded an average annual temperature of 65°F — about 1.3°F below the 30-year normal of 66°F. The hottest day reached 104°F in August; the coldest was 39°F in March. Total precipitation was 24 inches (wetter than usual). The wettest month was November.
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