Today | Weather | Tuesday, August 25, 2026
Active Weather Warnings

Weather in Rancho Cucamonga, California

07:34 AM
Now
Cloudy Weather
79° F
Feels Like 81°
Precipitation 0 %
Wind 2 mph
UV Index (0 - 11+) 2
Humidity 49 %
Today
Sunny Weather
Day 102°
Night 73°
Precipitation 0 %
Wind 8 mph
UV Index (0 - 11+) 9

Warning: High UV Index Today: 9

High risk of harm from unprotected sun exposure. Take precautions: wear a hat, sunglasses, and apply sunscreen regularly if you’ll be outdoors for extended periods.

Rancho Cucamonga Weather Forecast Updated

27 minutes ago
Last updated on
Weather Forecast History
Last Year's Weather on This Day (August 25, 2025)
Cloudy Night

Day

97°

Night

66°

Wind

5 mph

Precipitation

1 %

Air Quality in Rancho Cucamonga

NOW
32 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 7.37 µg/m³
PM10 18.09 µg/m³
O3 0.035 ppm
NO2 0.3 ppb
SO2 0.2 ppb
CO 0.07 ppm
NH3 0 µg/m³
NO 0.03 µg/m³
PM2.5 – Fine particles <2.5μm
PM10 – Inhalable particles <10μm
O3 – Ozone
NO2 – Nitrogen dioxide
SO2 – Sulfur dioxide
CO – Carbon monoxide
NH3 – Ammonia
NO – Nitric oxide

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

Show raw pollutant concentrations (µg/m³)
PM2.57.37 µg/m³
PM1018.09 µg/m³
O368.05 µg/m³
NO20.65 µg/m³
SO20.51 µg/m³
CO77.51 µg/m³
NH30 µg/m³
NO0.03 µg/m³

Weather Alerts and Warnings for Rancho Cucamonga

Severe Future Likely

Extreme Heat Watch

Extreme Heat Watch issued August 22 at 1:10PM PDT until August 28 at 8:00PM PDT by NWS San Diego CA
Aug 25, 10:00 AM Aug 28, 8:00 PM
WHAT: Temperatures 90 to 97 for Inland Orange County, 90 to 102
for the San Diego County Valleys, 98 to 106 for the Inland Empire
and 89 to 100 in the mountains. Temperatures increase another few
degrees into the middle and end of next week, making for a
prolonged and dangerous stretch of heat.

WHERE: Orange County Inland Areas, Riverside County Mountains,
San Bernardino and Riverside County Valleys-The Inland Empire, San
Diego County Mountains, San Diego County Valleys, and Santa Ana
Mountains and Foothills.

WHEN: For the Heat Advisory, until 10 AM PDT Tuesday. For the
Extreme Heat Watch, from Tuesday morning through Friday evening.

IMPACTS: Heat related illnesses increase significantly during
extreme heat events. Hot temperatures may cause heat illnesses.

ADDITIONAL DETAILS: Low temperatures 5 to 10 degrees above normal
will limit relief from the heat. Increasing temperatures into the
middle of next week will increase the threat of heat-related
illness across populations.
+ Read More
Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.
Updated: Aug 22, 5:12 PM Source: NWS Alert
Severe Expected Likely

Extreme Heat Warning

Extreme Heat Warning issued August 25 at 3:47AM PDT until August 28 at 8:00PM PDT by NWS San Diego CA
Aug 25, 3:47 AM Aug 28, 8:00 PM
WHAT: Dangerously hot conditions with high temperatures up to 112
expected. Overnight low temperatures will be mostly in the 70s.

WHERE: San Bernardino and Riverside County Valleys-The Inland
Empire County.

WHEN: Until 8 PM PDT Friday.
+ Read More
Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.
Updated: Aug 25, 7:06 AM Source: NWS Alert
Moderate Expected Likely

Heat Advisory

Heat Advisory issued August 24 at 10:04PM PDT until August 25 at 10:00AM PDT by NWS San Diego CA
Aug 24, 10:04 PM Aug 25, 10:00 AM
WHAT: For the Heat Advisory, temperatures up to 106. For the
Extreme Heat Warning, dangerously hot conditions with temperatures
up to 110 expected.

WHERE: San Bernardino and Riverside County Valleys-The Inland
Empire County.

WHEN: For the Heat Advisory, until 10 AM PDT Tuesday. For the
Extreme Heat Warning, from 10 AM Tuesday to 8 PM PDT Friday.

IMPACTS: Heat related illnesses increase significantly during
extreme heat events. Hot temperatures may cause heat illnesses.

ADDITIONAL DETAILS: Low temperatures 5 to 10 degrees above normal
will limit relief from the heat. Increasing temperatures into the
middle of next week will increase the threat of heat-related
illness across populations.
+ Read More
Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.
Updated: Aug 25, 2:40 AM Source: NWS Alert

Air Quality Alert

Air Quality Alert issued August 24 at 1:34PM PDT by NWS San Diego CA
Aug 24, 1:34 PM Aug 28, 8:00 PM
WHAT: The South Coast AQMD has issued an air quality alert due to
harmful levels of ozone pollution.
Visit https://www.aqmd.gov/alertinfo to check current and forecasted
air quality levels.

WHERE: in the the South Coast Air Basin and Coachella Valley.
Levels of ozone pollution can vary by time and location depending on
emissions and air pollution transport.

WHEN: from 1 PM Monday to 8 PM Friday. The highest ozone levels
typically occur in the afternoon and early-evening hours.

IMPACTS: Ozone air pollution can cause serious health problems,
including trouble breathing, asthma attacks, and lung damage.
Everyone can be affected, but sensitive groups such as people with
lung disease, older adults, people who are pregnant, children, and
those who spend a lot of time outdoors are at greater risk.
+ Read More
To protect your health, check air quality levels and act as needed: * When Air Quality Index (AQI) levels are "Unhealthy for Sensitive Groups" (orange), sensitive groups as specified above should limit extended or intense outdoor activity. * When AQI is "Unhealthy" (red), everyone may experience health impacts. Sensitive groups should avoid extended time outdoors. * When AQI is "Very Unhealthy" (purple), sensitive groups should avoid all outdoor physical activity. Everyone else should avoid extended or intense outdoor activity. * When AQI is "Hazardous" (maroon), everyone should avoid all outdoor physical activity. * ADDITIONAL DETAILS... To help keep indoor air clean when air quality is poor: * Keep windows and doors closed * Run your air conditioner and/or an air purifier * Do not use whole house fans or swamp coolers that bring in outside air if you have other methods to stay cool * Avoid other sources of pollution such as fireplaces, candles, incense, and grilling To help minimize outdoor ozone air pollution levels: * Limit the use of gasoline powered lawn and garden equipment until evening hours * Try to delay trips to the gas station and the use of household chemicals until the evening For the latest air quality forecasts and information, visit the website at aqmd.gov.
Updated: Aug 25, 7:06 AM Source: NWS Alert