Walnut Creek, California Weather
Coastal fog thickens at dawn. Day 77 of spring. Read this microseason across nine climate regions →
Walnut Creek weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 4Overcast——87°54°—
- FridayJun 5Overcast——90°60°+3°
- SaturdayJun 6Overcast——73°49°-17°
- SundayJun 7Overcast——78°47°+5°
- MondayJun 8Light Drizzle15%0.01″70°51°-8°
- TuesdayJun 9Overcast——66°50°-4°
- WednesdayJun 10Clear——80°47°+14°
PM2.5 at 6.3 µg/m³ (AQI 35) with a 0.78 fine-to-coarse ratio and 4 mph wind — combustion smoke trapped in calm air, not road dust. AQI down 7 over the last 6 hours (steady decline since this morning).
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.
What's driving it
PM × Wind × Precip
PM2.5 at 6.3 µg/m³ (AQI 35) with a 0.78 fine-to-coarse ratio and 4 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.78
- Wind
- calm
- 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).
A summer fog for fair, a winter fog for rain.
- Moonrise
- 6:34 AM
- Moonset
- 4:22 PM
- In sign
- ♒︎ Aquarius
Coastal fog thickens at dawn
Walnut Creek at a glance
- Today vs. normal: 8°F below the seasonal normal for this latitude
- 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 4, 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
Walnut Creek's warmest month is August (~74°F mean) and its coldest is January (~49°F). Rainfall peaks in January (3.2 inches) and bottoms out in July (0.0 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 49° | 3.2″ | 5 |
| February | 53° | 3.2″ | 6 |
| March | 57° | 2.3″ | 6 |
| April | 60° | 1.1″ | 3 |
| May | 65° | 0.5″ | 1 |
| June | 71° | 0.2″ | 0 |
| July | 73° | 0.0″ | 0 |
| August | 74° | 0.0″ | 0 |
| September | 72° | 0.1″ | 0 |
| October | 65° | 0.7″ | 1 |
| November | 56° | 1.6″ | 4 |
| December | 50° | 3.2″ | 6 |
Regional context
Walnut Creek sits within a hot-summer Mediterranean climate region — a cohort that shares similar temperature ranges, seasonal patterns, and growing conditions across nearby cities.
Similar climates: Los Angeles, CA, San Francisco, CA, San Diego, CA, Riverside, CA, Sacramento, CA.
Frequently asked
- When does it freeze in Walnut Creek?
- Walnut Creek's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Walnut Creek?
- January 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 Walnut Creek?
- August is typically warmest, averaging about 74°F.
- What is the coldest month in Walnut Creek?
- January is typically coldest, averaging about 49°F.
- When can I start a vegetable garden in Walnut Creek?
- 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 Walnut Creek get?
- Walnut Creek averages about 33 rainy days per year.
- What hardiness zone is Walnut Creek?
- Walnut Creek'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
Walnut Creek, California sits in a hot-summer Mediterranean climate zone. January means hover near 49°F while July averages 73°F — a 24°F seasonal swing.
Across the year, Walnut Creek receives about 16 inches of precipitation spread over roughly 33 rainy days.
The rhythm of the year is set by latitude (37.9°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.