Rancho Cucamonga, California Weather
Ceanothus blooms again. Day 93 of summer. Read this microseason across nine climate regions →
Rancho Cucamonga weather forecast — hour by hour, 7-day outlook, NOAA radar
Conditions updated 7:25 AM PDT · Open-Meteo
- TodaySep 21Clear later——80°63°—
- TuesdaySep 22Overcast——82°61°+2°
- WednesdaySep 23Partly Cloudy——92°60°+10°
- ThursdaySep 24Clear——92°77°0°
- FridaySep 25Overcast——92°75°0°
- SaturdaySep 26Overcast——92°76°0°
- SundaySep 27Overcast——88°74°-4°
Air quality now AQI 61 · Moderate
AQI 61 (Moderate), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 25.3 µg/m³ (AQI 81) with a 0.86 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 during the projected peak around 8 PM.
What's driving it
PM × Wind × Precip
PM2.5 at 25.3 µg/m³ (AQI 81) with a 0.86 fine-to-coarse ratio and 3 mph wind — combustion smoke trapped in stagnant air, not road dust.
- PM2.5/PM10
- 0.86
- 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
- 4:10 PM
- Moonset
- 1:34 AM
- In sign
- ♑︎ Capricorn
Ceanothus blooms again
Read this microseason across nine climate regions →
All 72 microseasons on the year wheel →
Rancho Cucamonga at a glance
- Today vs. normal: Today averages 72°F (high 80°F, low 63°F), 3°F below the 75°F normal for Sep 21
- Last frost: None in most years — 32°F in 41% of 1991–2020 years (NOAA station 8 km away)
- Microseason: Sep 21–25
- Planting calendar: September — plant lettuce, peas, spinach, radishes, beans, squash; harvest lettuce, peas, spinach, radishes, tomatoes, peppers, beans, summer squash, winter squash
16-Day Forecast — Rancho Cucamonga
- Mon80°63°3%
- Tue82°61°1%
- Wed92°60°0%
- Thu92°77°2%
- Fri92°75°2%
- Sat92°76°1%
- Sun88°74°2%
- Mon94°73°5%
- Tue97°78°6%
- Wed99°81°8%
- Thu102°85°5%
- Fri101°87°11%
- Sat99°84°13%
- Sun99°85°12%
- Mon97°83°10%
- Tue92°79°6%
Forecast data from Open-Meteo (CC BY 4.0).
Live wind & temperature near Rancho Cucamonga
Interactive wind and temperature map centered on Rancho Cucamonga — it loads in your browser. Open the full weather map.
Right now in the garden
Year-round growing
As of September 21, sowing here runs through the year. Freezes are uncommon, so there is no frost date to plan around; heat and rainfall set the calendar instead. This city's planting calendar for September: plant lettuce, peas, spinach, radishes, beans, and squash; harvest lettuce, peas, spinach, radishes, tomatoes, peppers, beans, summer squash, and winter squash.
Sun & seasons in Rancho Cucamonga
Rancho Cucamonga sits in San Bernardino County, where the year’s longest day runs 14h 26m of daylight and its shortest just 9h 52m — a swing of +4h 33m 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 48 miles to the W. The nearest town Rancho Cucamonga tracks is Ontario, roughly 6 miles to the SSW.
Air quality in Rancho Cucamonga
Air quality in Rancho Cucamonga’s county has trended cleaner since 2020; its cleanest year on record was 2023 (median AQI 71). See the full air-quality history for Rancho Cucamonga.
Planting calendar
| Month | Plant | Harvest |
|---|---|---|
| January | lettuce, peas, spinach, radishes | lettuce, peas, spinach, radishes |
| February | lettuce, peas, spinach, radishes | lettuce, peas, spinach, radishes |
| March | lettuce, peas, spinach, radishes | lettuce, peas, spinach, radishes |
| April | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash | lettuce, peas, spinach, radishes |
| May | spinach, radishes, tomatoes, peppers, beans, squash | lettuce, peas, spinach, radishes, summer squash |
| June | tomatoes, peppers, beans, squash | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, summer squash |
| July | lettuce, peas, tomatoes, peppers, beans, squash | tomatoes, peppers, beans, summer squash, winter squash |
| August | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash | tomatoes, peppers, beans, summer squash, winter squash |
| September | lettuce, peas, spinach, radishes, beans, squash | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, summer squash, winter squash |
| October | lettuce, peas, spinach, radishes | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, summer squash, winter squash |
| November | lettuce, peas, spinach, radishes | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, summer squash, winter squash |
| December | lettuce, peas, spinach, radishes | lettuce, peas, spinach, radishes |
A year in weather
Rancho Cucamonga peaks at about 80°F in August and bottoms near 52°F in January; February brings the heaviest rain (3.4 inches) and August the least (0.0 inches).
| Month | Mean temp | Precip |
|---|---|---|
| January | 52° | 3.3″ |
| February | 54° | 3.4″ |
| March | 57° | 3.0″ |
| April | 62° | 1.5″ |
| May | 67° | 0.5″ |
| June | 73° | 0.1″ |
| July | 79° | 0.1″ |
| August | 80° | 0.0″ |
| September | 76° | 0.1″ |
| October | 69° | 0.5″ |
| November | 59° | 1.6″ |
| December | 53° | 2.6″ |
Regional context
Similar climates Upland, CA, San Antonio Heights, CA, Ontario, CA
Drawing on modelled 1991-2020 normals (EC_Earth3P_HR model via Open-Meteo), Rancho Cucamonga's January averages 52°F and July 79°F — 27°F apart — while precipitation totals roughly 16.7 inches.
Rancho Cucamonga's moisture rides winter storm tracks: February brings 3.4 inches, while August sees only 0.0 inches in the dry warm season. That groups Rancho Cucamonga with places like Upland, CA, San Antonio Heights, CA and Ontario, CA on the same cool-season storm track.
Rancho Cucamonga rarely sees a hard freeze — its coldest month sits near 52°F — so planting spans most of the calendar. Heat peaks in August around 80°F, which confines cool-season crops to the shoulders of summer. Rancho Cucamonga beds by a wall stay warmer at night.
Similar climates: Upland, CA, San Antonio Heights, CA, Ontario, CA, Fontana, CA, Montclair, CA.
Frequently asked
- When does it freeze in Rancho Cucamonga?
- A freeze is the exception in Rancho Cucamonga: the nearest NOAA station hit 32°F in 41% of 1991–2020 years, too few for a frost date in Rancho Cucamonga.
- What is the rainy season in Rancho Cucamonga?
- Rainfall in Rancho Cucamonga peaks in February near 3.4 inches, out of about 17 inches annually.
- What is the warmest month in Rancho Cucamonga?
- On average August tops the year in Rancho Cucamonga at about 80°F.
- What is the coldest month in Rancho Cucamonga?
- The coldest stretch in Rancho Cucamonga falls in January, around 52°F on average.
- When can I start a vegetable garden in Rancho Cucamonga?
- Rancho Cucamonga has no frost date to wait for, so sowing runs year-round; lettuce and greens do best when Rancho Cucamonga's coldest month settles near 52°F.
- What hardiness zone is Rancho Cucamonga?
- Since January in Rancho Cucamonga averages 52°F, Rancho Cucamonga's USDA zone follows that floor — confirm it by ZIP.
- What is the 10-day forecast for Rancho Cucamonga?
- Rancho Cucamonga'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 Rancho Cucamonga?
- See this week's day-by-day rain chances for Rancho Cucamonga in the daily forecast above, and the next 24 hours in the hourly chart.
- What is the weather like right now in Rancho Cucamonga?
- Current conditions for Rancho Cucamonga and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
- How often is the Rancho Cucamonga forecast updated?
- The Rancho Cucamonga forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
- When are sunrise and sunset in Rancho Cucamonga?
- Today's sunrise and sunset times for Rancho Cucamonga 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 Rancho Cucamonga?
- The next few days in Rancho Cucamonga's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.
Rancho Cucamonga sits at 34.1°N; its climate zone is hot-summer Mediterranean (Köppen approximation).
ZIP codes in Rancho Cucamonga
- 91701
- 91729
- 91730
- 91737
- 91739