Diamond Bar weather by month
What a typical year looks like in Diamond Bar, California: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at ANAHEIM, 15 km from Diamond Bar; records cover 1989–2026.
The year at a glance
- Precipitation a year
- 13.5 in343 mm
- Snow a year
- Rare
- Last spring freeze
- Rare
- First fall freeze
- Rare
- Heating degree days
- 793
- Cooling degree days
- 1,812
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are 39°4° (heating, 99%) and 101°38° (cooling, 1%).
Month by month
Diamond Bar in January
Highs average 71°22° and lows 49°9°, with 3.2 in80 mm of precipitation in a typical January.
- Record high
- 95°35° (2003)
- Record low
- 30°−1° (2002)
- Heating degree days
- 176
- Cooling degree days
- 20
Diamond Bar in February
Highs average 71°22° and lows 49°10°, with 3.1 in77 mm of precipitation in a typical February.
- Record high
- 97°36° (2016)
- Record low
- 30°−1° (1990)
- Heating degree days
- 156
- Cooling degree days
- 20
Diamond Bar in March
Highs average 74°23° and lows 51°11°, with 1.8 in46 mm of precipitation in a typical March.
- Record high
- 100°38° (2026)
- Record low
- 37°3° (2002)
- Heating degree days
- 112
- Cooling degree days
- 36
Diamond Bar in April
Highs average 77°25° and lows 54°12°, with 0.7 in18 mm of precipitation in a typical April.
- Record high
- 106°41° (2004)
- Record low
- 38°3° (1999)
- Heating degree days
- 58
- Cooling degree days
- 68
Diamond Bar in May
Highs average 78°26° and lows 58°15°, with 0.41 in10 mm of precipitation in a typical May.
- Record high
- 106°41° (2004)
- Record low
- 45°7° (1999)
- Heating degree days
- 20
- Cooling degree days
- 116
Diamond Bar in June
Highs average 82°28° and lows 62°17°, with 0.11 in2.8 mm of precipitation in a typical June.
- Record high
- 106°41° (2016)
- Record low
- 50°10° (1995)
- Heating degree days
- 2
- Cooling degree days
- 203
Diamond Bar in July
Highs average 87°30° and lows 66°19°, with 0.11 in2.8 mm of precipitation in a typical July.
- Record high
- 107°42° (2006)
- Record low
- 54°12° (1999)
- Heating degree days
- 0
- Cooling degree days
- 347
Diamond Bar in August
Highs average 89°32° and lows 66°19°, with 0.01 in0.3 mm of precipitation in a typical August.
- Record high
- 106°41° (2022)
- Record low
- 52°11° (2002)
- Heating degree days
- 0
- Cooling degree days
- 384
Diamond Bar in September
Highs average 88°31° and lows 64°18°, with 0.15 in3.8 mm of precipitation in a typical September.
- Record high
- 112°44° (2024)
- Record low
- 51°11° (1991)
- Heating degree days
- 0
- Cooling degree days
- 329
Diamond Bar in OctoberThis month
Highs average 83°29° and lows 59°15°, with 0.62 in16 mm of precipitation in a typical October.
- Record high
- 107°42° (1991)
- Record low
- 44°7° (2009)
- Heating degree days
- 9
- Cooling degree days
- 206
Diamond Bar in November
Highs average 77°25° and lows 53°12°, with 1 in26 mm of precipitation in a typical November.
- Record high
- 102°39° (2010)
- Record low
- 33°1° (1994)
- Heating degree days
- 73
- Cooling degree days
- 70
Diamond Bar in December
Highs average 71°21° and lows 48°9°, with 2.4 in61 mm of precipitation in a typical December.
- Record high
- 91°33° (2010)
- Record low
- 32°0° (1998)
- Heating degree days
- 187
- Cooling degree days
- 13