Diablo, California Weather
Coastal fog thickens at dawn. Day 78 of spring. Read this microseason across nine climate regions →
Diablo weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 4Overcast——83°53°—
- FridayJun 5Clear——88°57°+5°
- SaturdayJun 6Overcast——70°47°-18°
- SundayJun 7Overcast——76°45°+6°
- MondayJun 8Heavy Drizzle16%0.10″59°48°-17°
- TuesdayJun 9Light Drizzle18%0.04″75°52°+16°
- WednesdayJun 10Clear——87°51°+12°
PM2.5 at 9.7 µg/m³ (AQI 52) with a 0.73 fine-to-coarse ratio and 6 mph wind — combustion smoke trapped in calm air, not road dust. AQI up 17 in the last 6 hours — air quality is degrading.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.
What's driving it
Ozone × UV × Sky
Ozone at AQI 46 — peak already passed at 1 PM under clear skies. Levels should ease through evening.
- Present
- AQI 46
- UV peak
- 1.0 at earlier today
- Sky at peak
- clear
- Projected peak
- AQI 46
PM × Wind × Precip
PM2.5 at 9.7 µg/m³ (AQI 52) with a 0.73 fine-to-coarse ratio and 6 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.73
- Wind
- light
- Recent rain
- 0h in last 6h
- Pattern
- stagnant smoke
Trends
Seven days of AQI and PM2.5.
Hourly air-quality data from the Copernicus Atmosphere Monitoring Service, charted across the past and next several days. Dashed lines mark the AQI breakpoints at 50 (Good → Moderate) and 100 (Moderate → Unhealthy for Sensitive Groups).
The higher the clouds, the finer the weather.
- Moonrise
- 7:05 AM
- Moonset
- 5:25 PM
- In sign
- ♒︎ Aquarius
Coastal fog thickens at dawn
Diablo at a glance
- Today vs. normal: 77°F — typical for the season
- Last frost: April 3 (climatological average for this latitude)
- Microseason: Jun 1–5
- Planting window: Harvest spring lettuce before it bolts. Sow heat-tolerant greens.
Right now in the garden
Peak growing season
As of June 5, the growing season is at its peak — frost is months away. Continue succession-planting beans and summer squash. Start fall brassicas (broccoli, cabbage, kale) from seed indoors for transplanting in late summer.
Planting calendar
| Month | Plant | Harvest |
|---|---|---|
| January | — | — |
| February | — | — |
| March | — | — |
| April | lettuce, peas, spinach, radishes | — |
| May | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| June | tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| July | tomatoes, peppers, beans, squash | tomatoes, beans, summer squash |
| August | — | tomatoes, beans, summer squash |
| September | fall brassicas, garlic (overwinter), carrots | tomatoes, beans, summer squash |
| October | fall brassicas, garlic (overwinter), carrots | winter squash, tomatoes (last) |
| November | — | — |
| December | — | — |
A year in weather
Diablo's warmest month is September (~67°F mean) and its coldest is December (~51°F). Rainfall peaks in December (3.2 inches) and bottoms out in July (0.0 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 51° | 2.9″ | 5 |
| February | 54° | 3.1″ | 7 |
| March | 56° | 2.4″ | 6 |
| April | 58° | 1.2″ | 3 |
| May | 61° | 0.6″ | 1 |
| June | 65° | 0.1″ | 0 |
| July | 66° | 0.0″ | 0 |
| August | 67° | 0.1″ | 0 |
| September | 67° | 0.1″ | 0 |
| October | 64° | 0.8″ | 2 |
| November | 56° | 1.5″ | 4 |
| December | 51° | 3.2″ | 6 |
Frequently asked
- When does it freeze in Diablo?
- Diablo's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Diablo?
- December is the wettest month with about 3.2 inches of rain on average; the city receives roughly 16 inches annually.
- What is the warmest month in Diablo?
- September is typically warmest, averaging about 67°F.
- What is the coldest month in Diablo?
- December is typically coldest, averaging about 51°F.
- When can I start a vegetable garden in Diablo?
- Cool-season crops (peas, lettuce) can be sown around the last spring frost (mid-April); warm-season crops (tomatoes, peppers) wait until 1–2 weeks after.
- How many rainy days does Diablo get?
- Diablo averages about 35 rainy days per year.
- What hardiness zone is Diablo?
- Diablo's USDA hardiness zone is determined by its lowest average winter temperature; check the USDA's online lookup with the city ZIP for the current zone designation.
Climate
Diablo, California sits in a hot-summer Mediterranean climate zone. January means hover near 51°F while July averages 66°F — a 15°F seasonal swing.
Across the year, Diablo receives about 16 inches of precipitation spread over roughly 35 rainy days.
The rhythm of the year is set by latitude (37.8°N), proximity to large water bodies, and elevation — all of which shape what grows here, when frost is likely, and what the weather story looks like day to day.