Sunnyvale, California Weather
Ceanothus blooms again. Day 93 of summer. Read this microseason across nine climate regions →
Sunnyvale weather forecast — hour by hour, 7-day outlook, NOAA radar
Conditions updated 7:24 AM PDT · Open-Meteo
- TodaySep 21Clear later——71°57°—
- TuesdaySep 22Mostly Clear——74°54°+3°
- WednesdaySep 23Clear——85°56°+11°
- ThursdaySep 24Overcast——84°65°-1°
- FridaySep 25Overcast——77°62°-7°
- SaturdaySep 26Overcast——81°62°+4°
- SundaySep 27Overcast——77°59°-4°
Air quality now AQI 50 · Good
AQI 50 (Good), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 8.6 µg/m³ (AQI 48) with a 0.77 fine-to-coarse ratio and 3 mph wind — combustion smoke trapped in stagnant air, not road dust.
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 8.6 µg/m³ (AQI 48) with a 0.77 fine-to-coarse ratio and 3 mph wind — combustion smoke trapped in stagnant air, not road dust.
- PM2.5/PM10
- 0.77
- 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).
September dries up ditches or breaks down bridges.
- Moonrise
- 4:37 PM
- Moonset
- 1:43 AM
- In sign
- ♑︎ Capricorn
Ceanothus blooms again
Read this microseason across nine climate regions →
All 72 microseasons on the year wheel →
Sunnyvale at a glance
- Today vs. normal: Today averages 64°F (high 71°F, low 57°F), 2°F below the 66°F normal for Sep 21
- Last frost: January 6 (1991–2020 median, NOAA station 3 km away)
- Microseason: Sep 21–25
- Planting calendar: September — plant tomatoes, peppers, beans, squash; harvest tomatoes, peppers, beans, summer squash, winter squash
16-Day Forecast — Sunnyvale
- Mon71°57°1%
- Tue74°54°1%
- Wed85°56°0%
- Thu84°65°0%
- Fri77°62°0%
- Sat81°62°0%
- Sun77°59°1%
- Mon81°60°1%
- Tue90°65°1%
- Wed94°69°3%
- Thu88°72°1%
- Fri92°77°6%
- Sat96°75°0%
- Sun91°71°0%
- Mon82°63°0%
- Tue79°63°0%
Forecast data from Open-Meteo (CC BY 4.0).
Live wind & temperature near Sunnyvale
Interactive wind and temperature map centered on Sunnyvale — it loads in your browser. Open the full weather map.
Right now in the garden
Peak growing season
As of September 21, the growing season is at its peak — the first frost (around December 23) is weeks away. Fall transplants go in about 10–12 weeks before the first frost, September 30 to October 14 here. This city's planting calendar for September: plant tomatoes, peppers, beans, and squash; harvest tomatoes, peppers, beans, summer squash, and winter squash.
Sun & seasons in Sunnyvale
Sunnyvale sits in Santa Clara County, where the year’s longest day runs 14h 44m of daylight and its shortest just 9h 35m — a swing of +5h 10m between the June and December solstices. Clocks spring forward on Sunday, March 8, 2026 and fall back on Sunday, November 1, 2026.
Los Angeles, the state’s largest city, lies about 304 miles to the SE. The nearest town Sunnyvale tracks is Santa Clara, roughly 3 miles to the ESE.
Air quality in Sunnyvale
Air quality in Sunnyvale’s county has trended cleaner since 2020; its cleanest year on record was 2023 (median AQI 43). See the full air-quality history for Sunnyvale.
Planting calendar
| Month | Plant | Harvest |
|---|---|---|
| January | lettuce, peas, spinach, radishes | lettuce, spinach, radishes, fall brassicas, carrots |
| February | — | lettuce, peas, spinach, radishes |
| March | — | lettuce, peas, spinach |
| April | — | peas |
| May | tomatoes, peppers, beans, squash | garlic |
| June | tomatoes, peppers, beans, squash | summer squash |
| July | beans, squash | tomatoes, peppers, beans, summer squash |
| August | tomatoes, peppers, beans, squash | tomatoes, peppers, beans, summer squash, winter squash |
| September | tomatoes, peppers, beans, squash | tomatoes, peppers, beans, summer squash, winter squash |
| October | beans, squash, fall brassicas, carrots | tomatoes, peppers, beans, summer squash, winter squash |
| November | garlic (overwinter) | tomatoes, peppers, beans, summer squash, winter squash |
| December | lettuce, peas, spinach, radishes, garlic (overwinter) | tomatoes, peppers, beans, summer squash, winter squash, fall brassicas, carrots |
A year in weather
Sunnyvale's warmest month is August (~68°F mean) and its coldest is December (~51°F). Rainfall peaks in February (3.2 inches) and bottoms out in July (0.0 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 51° | 3.0″ | 6 |
| February | 53° | 3.2″ | 7 |
| March | 56° | 2.5″ | 6 |
| April | 58° | 1.2″ | 4 |
| May | 62° | 0.5″ | 2 |
| June | 65° | 0.2″ | 0 |
| July | 67° | 0.0″ | 0 |
| August | 68° | 0.0″ | 0 |
| September | 67° | 0.1″ | 0 |
| October | 63° | 0.7″ | 2 |
| November | 55° | 1.6″ | 4 |
| December | 51° | 3.0″ | 7 |
Regional context
Similar climates Mountain View, CA, Santa Clara, CA, Los Altos, CA
By the nearest station's NOAA NCEI 1991-2020 normals, Sunnyvale sees 51°F Januarys and 67°F Julys, a 17°F range, plus around 15.9 inches of precipitation across 37 days.
Precipitation in Sunnyvale peaks in the cool season: February averages 3.2 inches across 6.8 storm-fed days, while July bottoms out at 0.0 inches over just 0.0 rainy days. That groups Sunnyvale with places like Mountain View, CA, Santa Clara, CA and Los Altos, CA on the same cool-season storm track.
The cool-season window in Sunnyvale starts at January 6, when nights stop freezing — think lettuce, chard, arugula, and mustard greens. Hold Sunnyvale's tender crops — tomatoes, peppers, basil — until 10-14 days past Sunnyvale's last frost. Sunnyvale's window closes around December 23 as Sunnyvale's overnight lows return below freezing. In about half of years, Sunnyvale's last freeze comes after January 6.
Similar climates: Mountain View, CA, Santa Clara, CA, Los Altos, CA, Loyola, CA, Cupertino, CA.
Frequently asked
- When does it freeze in Sunnyvale?
- Sunnyvale's last spring frost lands near January 6, and in Sunnyvale the first fall frost follows around December 23.
- What is the rainy season in Sunnyvale?
- Sunnyvale sees its heaviest rain in February (around 3.2 inches), part of roughly 16 inches a year.
- What is the warmest month in Sunnyvale?
- On average August tops the year in Sunnyvale at about 68°F.
- What is the coldest month in Sunnyvale?
- The coldest stretch in Sunnyvale falls in December, around 51°F on average.
- When can I start a vegetable garden in Sunnyvale?
- Hardy spring crops go in near January 6 in Sunnyvale; tender peppers and squash wait 10–14 days.
- How many rainy days does Sunnyvale get?
- Sunnyvale averages about 37 days with measurable rain or snow each year.
- What hardiness zone is Sunnyvale?
- Because Sunnyvale bottoms near 51°F in December, that winter low sets Sunnyvale's USDA zone — verify by ZIP.
- What is the 10-day forecast for Sunnyvale?
- Sunnyvale's extended outlook — daily high and low temperatures and precipitation chances for each upcoming day — is in the daily forecast above.
- Will it rain this week in Sunnyvale?
- See this week's day-by-day rain chances for Sunnyvale in the daily forecast above, and the next 24 hours in the hourly chart.
- What is the weather like right now in Sunnyvale?
- Current conditions for Sunnyvale and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
- How often is the Sunnyvale forecast updated?
- The Sunnyvale forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
- When are sunrise and sunset in Sunnyvale?
- Today's sunrise and sunset times for Sunnyvale are in the Almanac section above, along with civil dawn, civil dusk, and day length. Day length is longest near the summer solstice and shortest near the winter solstice.
- How accurate is the weather forecast for Sunnyvale?
- The next few days in Sunnyvale's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.
Sunnyvale sits at 37.4°N; its climate zone is hot-summer Mediterranean (Köppen approximation).
ZIP codes in Sunnyvale
- 94085
- 94086
- 94087
- 94088
- 94089