Weather in Rancho Cucamonga, California
Fog and sun in daily rhythm. Day 58 of spring. Read this microseason across nine climate regions →
- TodayMay 16Light Drizzle—70°56°
- SundayMay 17Foggy—74°52°
- MondayMay 18Overcast—82°53°
- TuesdayMay 19Partly Cloudy—86°63°
- WednesdayMay 20Overcast—86°67°
- ThursdayMay 21Overcast—84°63°
- FridayMay 22Clear—85°64°
- PM 2.5
- 12.2 μg/m³
- PM 10
- 19.3 μg/m³
- NO₂
- 2.0 μg/m³
- Ozone
- 117.0 μg/m³
- UV Index
- 3.3 Moderate
Flowers blooming in late autumn, a sure sign of a bad winter coming.
- Moonrise
- 12:16 PM
- Moonset
- 2:02 AM
- In sign
- ♉︎ Taurus
Fog and sun in daily rhythm
Rancho Cucamonga at a glance
- Today vs. normal: 9°F below the seasonal normal for this latitude
- Last frost: March 12 (climatological average for this latitude)
- Microseason: 28 of 72, May 16–20
- Planting window: Direct sow okra, melons, and southern peas. Thin carrot rows.
Right now in the garden
Peak growing season
As of May 16, 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 | lettuce, peas, spinach, radishes | — |
| April | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash | — |
| May | tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| June | tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| July | — | tomatoes, beans, summer squash |
| August | — | tomatoes, beans, summer squash |
| September | — | tomatoes, beans, summer squash |
| October | fall brassicas, garlic (overwinter), carrots | winter squash, tomatoes (last) |
| November | fall brassicas, garlic (overwinter), carrots | — |
| December | — | — |
A year in weather
August brings Rancho Cucamonga's peak warmth with mean temperatures around 81°F, while December delivers the year's coldest conditions at 56°F. Precipitation follows a Mediterranean pattern, with February receiving the most rainfall at 2.5 inches and June seeing just 0.1 inches.
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 56° | 2.2″ | 4 |
| February | 57° | 2.5″ | 5 |
| March | 60° | 1.6″ | 3 |
| April | 64° | 0.6″ | 1 |
| May | 68° | 0.2″ | 1 |
| June | 74° | 0.1″ | 0 |
| July | 80° | 0.1″ | 0 |
| August | 81° | 0.1″ | 0 |
| September | 77° | 0.1″ | 0 |
| October | 69° | 0.4″ | 1 |
| November | 61° | 0.7″ | 2 |
| December | 56° | 1.4″ | 3 |
Regional context
As part of the broader hot-summer Mediterranean climate region, Rancho Cucamonga shares temperature ranges, seasonal patterns, and growing conditions with surrounding cities in this climate zone.
Similar climates: Los Angeles, CA, San Francisco, CA, San Diego, CA, Riverside, CA, Sacramento, CA.
Naturalist notes
California poppies typically begin their spring bloom in late March as soil temperatures warm.
Allen's hummingbirds start their northward migration through the region during April and May.
Frequently asked
- When does it freeze in Rancho Cucamonga?
- Spring's final frost usually occurs around mid-March in Rancho Cucamonga, while the first fall frost returns around mid-December.
- What is the rainy season in Rancho Cucamonga?
- February brings the heaviest rainfall, averaging 2.5 inches, while the city's total annual precipitation reaches roughly 10 inches.
- What is the warmest month in Rancho Cucamonga?
- August typically records the year's highest temperatures, with averages near 81°F.
- What is the coldest month in Rancho Cucamonga?
- December marks the coldest period, with temperatures averaging around 56°F.
- When can I start a vegetable garden in Rancho Cucamonga?
- Plant cool-season crops like peas and lettuce around the last spring frost in mid-March, but wait 1–2 weeks later for warm-season varieties such as tomatoes and peppers.
- How many rainy days does Rancho Cucamonga get?
- The city experiences approximately 19 rainy days each year.
- What hardiness zone is Rancho Cucamonga?
- For Rancho Cucamonga's current USDA hardiness zone, use the USDA's online lookup tool with the city's ZIP code, as the zone reflects the area's lowest average winter temperatures.
Climate
Rancho Cucamonga, California experiences a hot-summer Mediterranean climate. Winter temperatures in January hover near 56°F, while July brings averages of 80°F — creating a 23°F seasonal swing.
Annual precipitation totals about 10 inches, falling across roughly 19 rainy days throughout the year.
Geography shapes the local weather patterns through three key factors: latitude (34.1°N), proximity to large water bodies, and elevation. These elements determine plant growth cycles, frost timing, and daily weather conditions.