Diamond Bar, CA climate
Diamond Bar has warm winters and warm summers, with very little rain. A typical July afternoon reaches 89°, a January night drops to 45°, and snow is almost unheard of.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Diamond Bar feels like
Winter
Spring
Summer
Fall
Diamond Bar weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 68° | 45° | 3.6" | 0 | 6 | 0 | 53° – 62° |
| February | 68° | 46° | 4.0" | 0 | 6 | 0 | 50° – 67° |
| March | 71° | 48° | 2.3" | 0 | 5 | 0 | 54° – 67° |
| April | 75° | 50° | 0.9" | 0 | 3 | 0 | 57° – 66° |
| May | 77° | 54° | 0.4" | 0 | 2 | 0 | 61° – 72° |
| June | 83° | 58° | 0.1" | 0 | 1 | 0 | 66° – 76° |
| July | 89° | 63° | 0.0" | 0 | 0 | 0 | 73° – 81° |
| August | 91° | 64° | 0.0" | 0 | 0 | 0 | 74° – 81° |
| September | 88° | 62° | 0.1" | 0 | 0 | 0 | 71° – 79° |
| October | 81° | 56° | 0.6" | 0 | 2 | 0 | 64° – 74° |
| November | 74° | 49° | 0.9" | 0 | 3 | 0 | 55° – 66° |
| December | 67° | 44° | 2.4" | 0 | 5 | 0 | 52° – 61° |
| Year | 78° | 53° | 15.3" | 0.0" | 33 | 0 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Diamond Bar
Diamond Bar gets 15 inches of rain and melted snow a year. February is the wettest month and August the driest. Rain or snow falls on about 33 days a year.
A year-round growing season
Heating and cooling a home in Diamond Bar
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Diamond Bar, 49% of that work is heating and 51% is cooling.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
Diamond Bar and its neighbors
Diamond Bar borders 4 towns with climate data. January nights across them vary by 2.7°. Pomona has both the coldest January nights (44°) and the hottest July afternoons (90°). Diamond Bar’s January low is 45° and its July high 89°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Diamond Bar compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Diamond Bar averaged 2.7° warmer than the 1900s. The biggest change is in January (+3.6°). The shift is larger than in 100% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Diamond Bar’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. February swings the most: between 1991 and 2020 its average temperature ranged from 50° to 67°. August is the most reliable, staying within 7°.
Common questions about Diamond Bar’s climate
What is the coldest month in Diamond Bar?
December, with a typical high of 67° and a low of 44°.
What is the hottest month in Diamond Bar?
August, with a typical high of 91° and a low of 64°. About 71 days a year reach 90°.
How much snow does Diamond Bar get?
Almost none. A normal year brings 0.0 inches.
When is the first frost in Diamond Bar?
Frost is uncommon. Only 65% of years see a night at 32° or below.
What is the rainiest month in Diamond Bar?
February, with 4.0 inches of rain and melted snow. The year totals 15 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Diamond Bar itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Covina City Yard Fc387b, CA (7 mi, snow) and Pomona/fairplex, CA (6 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.