Diamond Bar in Winter
In winter (December, January and February), Diamond Bar sees average daytime highs around 63°F and overnight lows near 45°F, with 10.1 in of rain over about 18 wet days across the season. It is the coldest season of the year and the wettest season of the year.
Across winter, daytime highs hold fairly steady around 63°F. The sky is clear or mostly clear about 48% of the time across winter, and the air most often feels dry.
Winter is Diamond Bar's weakest season of the year to visit on our travel score. For the whole year in context, see Diamond Bar's year-round climate.
- Avg daytime high
- 63°F
- coldest season of the year
- Avg overnight low
- 45°F
- Rainfall
- 10.1 in
- 18 wet days
- Avg wind
- 3 mph
- Travel score
- 6.2
- weakest season of the year
- Months
- Dec · Jan · Feb
Temperature in Diamond Bar in Winter
Across winter, daytime highs hold fairly steady around 63°F.
A typical winter day in Diamond Bar reaches about 63°F and drops to 45°F overnight. The warmest of the three months is February, the coolest December.
Diamond Bar weather by month
How the three winter months (December, January and February) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 63° / 44° | 3.6 | 5.9 | 10 | 6.2 |
| Feb | 63° / 46° | 4.0 | 6.6 | 10.7 | 6.2 |
| Mar | 66° / 48° | 2.4 | 6.3 | 11.7 | 6.8 |
| Apr | 70° / 51° | 1.0 | 3.7 | 12.8 | 7.8 |
| May | 74° / 55° | 0.4 | 2.2 | 13.7 | 8.6 |
| Jun | 79° / 59° | 0.1 | 0.3 | 14.2 | 8.9 |
| Jul | 85° / 64° | 0.1 | 0.5 | 14 | 7.1 |
| Aug | 87° / 65° | 0.0 | 0.2 | 13.3 | 6.5 |
| Sep | 84° / 63° | 0.2 | 0.9 | 12.2 | 7.4 |
| Oct | 78° / 57° | 0.7 | 2.6 | 11.1 | 8.7 |
| Nov | 69° / 49° | 1.0 | 2.8 | 10.2 | 8.0 |
| Dec | 62° / 44° | 2.5 | 5.3 | 9.8 | 6.3 |
Cloud cover in Winter
The sky is clear or mostly clear about 48% of the time across winter.
Chance of precipitation in Winter
Diamond Bar gets around 10.1 in of rain over 18 wet days across winter. The line is the day-by-day chance of measurable precipitation.
Humidity in Winter
Most of winter feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Winter
Winds average 3 mph across winter.
Sunrise & sunset in Winter
Daylight runs from about 9 h 54 min in early December to 11 h 12 min by late February. The lit band spans sunrise to sunset each day.
Solar energy in Winter
Average shortwave solar energy reaching the ground each day across winter, about 3.3 kWh/m².
Is winter a good time to visit Diamond Bar?
Our two travel scores rate winter for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
winter is a reasonable time to visit Diamond Bar for sightseeing.
What to pack for Diamond Bar in Winter
From winter's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In winter, Diamond Bar sees daytime highs around 63°F and nights near 45°F. Worth packing: a warm layer. About 18 days see rain.
Sea temperature near Diamond Bar in Winter
The nearest coast averages about 60°F across winter — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 28 mi away) is warmest in August at about 69°F and coldest in February near 59°F.
It's comfortable for a long swim from Jul 13 to Sep 28 — about 2.6 months when the water holds above 68°F.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°F) | 59 | 59 | 59 | 60 | 63 | 65 | 68 | 69 | 69 | 67 | 64 | 60 |
| Comfort | Cool | Cool | Cool | Cool | Cool | Cool | Refreshing | Refreshing | Refreshing | Cool | Cool | Cool |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 59 | Cool |
| Feb | 59 | Cool |
| Mar | 59 | Cool |
| Apr | 60 | Cool |
| May | 63 | Cool |
| Jun | 65 | Cool |
| Jul | 68 | Refreshing |
| Aug | 69 | Refreshing |
| Sep | 69 | Refreshing |
| Oct | 67 | Cool |
| Nov | 64 | Cool |
| Dec | 60 | Cool |
UV index in Diamond Bar in Winter
Clear-sky midday UV across winter averages around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Diamond Bar peaks around July 11 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 16 at about 3 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 11 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 4 | 5 | 5 | 8 | 8 | 11 | 11 | 10 | 8 | 6 | 3 | 3 |
| Level | Moderate | Moderate | Moderate | Very high | Very high | Extreme | Extreme | Extreme | Very high | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 4 | Moderate |
| Feb | 5 | Moderate |
| Mar | 5 | Moderate |
| Apr | 8 | Very high |
| May | 8 | Very high |
| Jun | 11 | Extreme |
| Jul | 11 | Extreme |
| Aug | 10 | Extreme |
| Sep | 8 | Very high |
| Oct | 6 | High |
| Nov | 3 | Moderate |
| Dec | 3 | Moderate |
Air quality in Diamond Bar in Winter
Average fine-particle pollution (PM2.5) through the year — so you can see where winter falls, not just the annual average.
Air quality in Diamond Bar is worst in September — around 49 µg/m³ PM2.5 (poor), about 4.0× the cleanest month (May, 12 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 18 | 19 | 19 | 17 | 12 | 17 | 19 | 32 | 49 | 21 | 21 | 18 |
| Level | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Poor | Moderate | Moderate | Moderate |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 18 | Moderate |
| Feb | 19 | Moderate |
| Mar | 19 | Moderate |
| Apr | 17 | Moderate |
| May | 12 | Moderate |
| Jun | 17 | Moderate |
| Jul | 19 | Moderate |
| Aug | 32 | Moderate |
| Sep | 49 | Poor |
| Oct | 21 | Moderate |
| Nov | 21 | Moderate |
| Dec | 18 | Moderate |
Where is Diamond Bar?
Diamond Bar sits at 34.0°N, 117.8°W, 696 ft above sea level, in United States. The nearest listed city is Walnut, 3.1 mi away.
Topography around Diamond Bar
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Diamond Bar.
Within 2 miles, the terrain around Diamond Bar has significant variations in elevation — a maximum elevation change of 892 ft around an average of 846 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,077 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 10,010 ft.
The land around Diamond Bar is covered by artificial surfaces (53%) within 2 miles, artificial surfaces (58%) within 10 miles, and artificial surfaces (27%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Diamond Bar (34.0286°, -117.8103°, elevation 696 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google.