Mt Diablo Junction, CA Climate: Temperature & Rain by Month
Explore NOAA NCEI's 1991–2020 climate normals → and a clearly labeled PlainClimate comfort calculation
30-year climate normals (1991-2020) from Mt Diablo Junction's primary NOAA station, MT DIABLO JUNCTION.
The climate verdict for Mt Diablo Junction
A compact 24.6°F seasonal swing gives Mt Diablo Junction, California a steadier-than-extreme annual shape. NOAA reports an annual average of 58°F. It scores 87/100 for climate comfort (excellent), putting it in the top third of station-mapped location scores and exceeding 87% of them.
- 58°F
- yearly average temperature, NOAA normal
- 87/100
- comfort score, above 87% of station-mapped location scores
- 26.1"
- annual precipitation · 1" snow
- 289 days
- frost-free growing season
Mt Diablo Junction: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USC00045915 · Mt Diablo Junction, CA 58°F mean · 26.1" precip
TEMP-MILD · RANK-UPPER · PHOTO-FINISH · PRCP-MID · SWING-NARROW · COMF-TOP · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-MILD 58°F
- RANK-UPPER #4,803
- PHOTO-FINISH ≈ Canelo
- PRCP-MID 26.1"
- SWING-NARROW 25°F
- COMF-TOP 87/100
- LOAD-HEAT 3,309 HDD
- STN-1 USC00045915
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Canelo, AZ ( -0.1 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every CA station list.
- Hot Dobbins, CA 59°F
- Mt Diablo Junct… (this station) 58°F
- Cold Orleans, CA 58°F
- Near Canelo, AZ 58°F
- Near Julian Cdf, CA 58°F
Climate Living Index · Mt Diablo Junction
Mt Diablo Junction: 84/100 · grade B
Mt Diablo Junction publishes 5 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 1 missing weight rescale to 100.
PlainClimate-derived for Mt Diablo Junction, not an official NOAA rating. Rankings still use Comfort Score 87/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Normal heat + freeze calendar | 0 calendar days | 100/100 · A |
| Frost-free season | 289 days/year | 99/100 · A |
| Snowfall burden | 0.7 inches/year | 85/100 · A |
| Annual temperature balance | 58.4°F · 9.1° from 67.5°F | 71/100 · B |
| Precipitation balance | 26.1 in · 8.9 from 35 in | 68/100 · C |
Mt Diablo Junction · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Mt Diablo Junction is a temperate Köppen climate: Csa
Coldest-month mean 47.4°F and warmest-month mean 72.0°F place this station in temperate, dry-summer, hot summer climates (Csa). Class Csa is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: temperate, specifically temperate, dry-summer, hot summer.
- Köppen code
- Csa
- Group
- Temperate
- Warmest month
- 72.0°F
- Coldest month
- 47.4°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · heating-led station
Where Mt Diablo Junction sits across the climate record
Three NOAA fields for Mt Diablo Junction's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- Top 30% warmest
- Among 6,861 stations, Mt Diablo Junction sits in the warmer third of annual means.
- Annual precipitation
- 36th percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- Narrower than 95%
- Warmest-to-coldest month gap for Mt Diablo Junction is compact versus 6,861 complete station-years.
How Mt Diablo Junction compares across U.S. station-mapped locations
Mt Diablo Junction's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
87 Top 13% score exceeds 87% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). Below this entry.
- 30–40: 280 station-mapped locations (5%). Below this entry.
- 40–50: 1,113 station-mapped locations (18%). Below this entry.
- 50–60: 1,329 station-mapped locations (21%). Below this entry.
- 60–70: 1,236 station-mapped locations (20%). Below this entry.
- 70–80: 650 station-mapped locations (11%). Below this entry.
- 80–90: 921 station-mapped locations (15%). This entry sits in this band.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Mt Diablo Junction's measured station temperature trend
MethodologyAcross 58 complete annual observations from 1953 to 2025, MT DIABLO JUNCTION warmed at a fitted rate of 0.27°C per decade. The line shows the fitted change relative to its first year, not raw year-to-year temperatures or a forecast.
- Mt Diablo Junction primary station fitted change +0.27 °C/decade
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Snow | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|---|
| January | 54°F (12°C) | 42°F (5°C) | 48°F (9°C) | 5.1" | 0.1" | 4.3 | 0.0 |
| February | 55°F (13°C) | 42°F (5°C) | 48°F (9°C) | 4.9" | 0.5" | 3.8 | 0.0 |
| March | 58°F (14°C) | 43°F (6°C) | 50°F (10°C) | 3.7" | 0.1" | 2.5 | 0.0 |
| April | 62°F (17°C) | 44°F (7°C) | 53°F (12°C) | 1.9" | 0.0" | 1.8 | 0.0 |
| May | 68°F (20°C) | 49°F (10°C) | 59°F (15°C) | 1.1" | 0.0" | 0.0 | 0.8 |
| June | 76°F (24°C) | 55°F (13°C) | 66°F (19°C) | 0.3" | 0.0" | 0.0 | 3.7 |
| July | 83°F (28°C) | 62°F (16°C) | 72°F (22°C) | 0.0" | 0.0" | 0.0 | 7.5 |
| August | 83°F (28°C) | 61°F (16°C) | 72°F (22°C) | 0.0" | 0.0" | 0.0 | 7.9 |
| September | 80°F (27°C) | 60°F (15°C) | 70°F (21°C) | 0.1" | 0.0" | 0.0 | 5.8 |
| October | 72°F (22°C) | 54°F (12°C) | 63°F (17°C) | 1.2" | 0.0" | 0.0 | 1.3 |
| November | 60°F (16°C) | 46°F (8°C) | 53°F (12°C) | 2.6" | 0.0" | 1.9 | 0.0 |
| December | 53°F (12°C) | 41°F (5°C) | 47°F (9°C) | 5.1" | 0.0" | 4.5 | 0.0 |
The year, day by day
The calendar barely moves in Mt Diablo Junction: no date carries a normal high of 90°F or a normal low at freezing. The year runs between 41°F near December 16 and 83°F near July 21.
No freezing date
Not one calendar date in the 1991–2020 record carries a normal low at or below 32°F. The coldest normal low of the year is 41°F around December 16.
Where the wet dates fall
The likeliest wet date is February 19, when 39% of years recorded at least a hundredth of an inch. The driest is July 28 at 1%. Summed across the calendar, that is about 69 wet dates a year.
The widest day
August 14 carries the biggest normal gap between afternoon and dawn, 22°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Mt Diablo Junction.
Where Mt Diablo Junction Stands Nationally
Days and nights track unusually close together; the widest normal swing, about 22°F, is narrower than most stations record.
Mt Diablo Junction earns one nationally notable standing (outer quintile) against 6,860 NOAA 1991–2020 normals stations, middle-of-the-pack metrics stay silent here.
Monthly Precipitation
Average monthly rainfall and snowfall
Snow: 0.1"
11.8 days with precipitation
Snow: 0.5"
11.1 days with precipitation
Snow: 0.1"
10.2 days with precipitation
6.7 days with precipitation
4.4 days with precipitation
1.3 days with precipitation
0.3 days with precipitation
0.4 days with precipitation
0.9 days with precipitation
3.4 days with precipitation
7.4 days with precipitation
10.5 days with precipitation
Mt Diablo Junction's wet season runs through the cold months
December, January and February carry 58% of the year's precipitation here, while June through August contribute 1%. That is the cool-season-dominant pattern of the West Coast and the higher inland West, where storm tracks swing south in winter and summer turns dry; the thermometer meanwhile shows an unusually narrow 24.6°F seasonal spread.
- Wettest month
- December, 5.1"
- Driest month
- July, 0.0"
- Wettest three months
- December, January, February (58% of the year)
Shares are computed from this station's own 1991-2020 monthly precipitation normals. A cool-season label means the December-February share reaches 35%. Where snow falls, the monthly figures above report liquid-equivalent precipitation, so a wet winter month is not necessarily a rainy one.
When it rains in Mt Diablo Junction, it arrives in quantity
26.1" of precipitation falls across only about 68 wet days here, averaging 0.38 inches each. Fewer days carry more water: the year's total is delivered in comparatively heavy events rather than persistent damp.
- Days with measurable precipitation
- about 68 a year, 19% of all days
- Average depth per wet day
- 0.38 inches
- Most wet days
- January, about 12
- Fewest wet days
- July, about 0
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year, and a per-day average is not a forecast of any individual storm.
Snow reaches Mt Diablo Junction, but rarely amounts to much
The normals record 0.7 inches of snow a year here, most likely in February. That is a real but marginal amount: enough that snow is part of the local record, not enough to define the winter.
A figure in this range usually reflects a handful of events that melt quickly rather than a season of accumulation; about 0 days a year record any measurable snow at all.
NOAA 1991-2020 normals. An average across thirty years can smooth away a single heavy winter, so a small annual figure does not mean a significant snowfall is impossible.
Frost Dates & Growing Season
First Fall Freeze
December 22
50% probability date
Last Spring Freeze
March 8
50% probability date
Growing Season
289 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
3,309
Higher = more heating needed
Cooling Degree Days
925
Higher = more cooling needed
Warmest Month
July
Coldest Month
December
Nationwide similar cities
Other rankable U.S. places outside CA closest to Mt Diablo Junction on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (58°F here).
- Camargo, OK 58°F · 0.0°F off
- Cornelia, GA 58°F · 0.0°F off
- Dayton, TN 58°F · 0.0°F off
- Decatur, TN 58°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (26.1" here), excluding temperature-peer places.
- Rocksprings, TX 26.0" · 0.0" off
- Ewing, NE 26.1" · 0.0" off
- Orr, MN 26.0" · 0.0" off
- Webster, SD 26.1" · 0.0" off
Data-derived climate profile
How Mt Diablo Junction's climate pattern fits together
heating led · moderate · low swing
Heating is the larger measured load in Mt Diablo Junction, at 3,309 degree days versus 925 for cooling. Unlike a strongly continental record, however, its 24.6°F month-to-month range is compact; persistent cool-season demand matters more than a dramatic summer-to-winter reversal.
The frost-free window extends for about 289 days. That is a long calendar measure, but it is not a forecast and does not combine heat, rainfall, soil, or local elevation into a planting recommendation.
Temperature varies within a narrow 24.6°F band across the normal year. July and December mark the typical warm and cold ends of the calendar. The annual average is 58°F. Monthly rows still matter, but they refine a steady profile rather than reveal two climatic extremes.
Mt Diablo Junction's 26.1 inches of annual precipitation falls in PlainClimate's middle band, so “wet” or “dry” is not the leading description. Annual snowfall totals 0.7 inches. Temperature balance and the calendar distribution carry more information than the annual moisture label alone.
These labels group NOAA 1991-2020 normals from Mt Diablo Junction's primary station, so the winter figures are a thirty-year average and not a floor: a single hard season can run well below them. Treat each band as a descriptive range for Mt Diablo Junction, not an official NOAA class or a year-ahead forecast.
Questions about Mt Diablo Junction's climate
How much rain does Mt Diablo Junction get? ▼
How much energy does heating and cooling require in Mt Diablo Junction? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Mt Diablo Junction's primary station: MT DIABLO JUNCTION (USC00045915). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The conservative exact name-and-state crosswalk finds no Census place match, so PlainClimate treats this as a station-mapped location and does not claim it is a municipality. No exact Gazetteer row for Mt Diablo Junction; facility counts that depend on place identity are therefore an upper bound, not a municipal census.
On this page every temperature, precipitation, and derived score for Mt Diablo Junction comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.