Today | Weather | Tuesday, March 17, 2026

Active Weather Warnings

Weather in Ontario, California

12:21 AM

Now

72° F

Feels Like 70°

Precipitation 0 %

Wind 6 mph

Humidity 38 %

Today

Day 99°

Night 63°

Precipitation 0 %

Wind 8 mph

UV Index (0 - 11+) 6

Ontario Weather Forecast Updated

44 minutes ago

Last updated on March 16, 2026 at 11:37 PM

Weather Forecast History

Last Year's Weather on This Day (March 17, 2025)

Day

66°

Night

43°

Wind

8 mph

UV Index

Precipitation

81 %

Air Quality in Ontario

NOW

58 AQI

Moderate air quality Dominant pollutant: PM_2.5

Pollutant Concentrations:

PM_2.5 15.96 µg/m³

PM₁₀ 21.97 µg/m³

O₃ 0.045 ppm

NO₂ 0.9 ppb

SO₂ 0.2 ppb

CO 0.14 ppm

NH₃ 0.03 µg/m³

NO 0 µg/m³

PM_2.5 – 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 acceptable; however, for some pollutants, there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.

Show raw pollutant concentrations (µg/m³)

PM_2.5 – 15.96 µg/m³

PM₁₀ – 21.97 µg/m³

O₃ – 89.22 µg/m³

NO₂ – 1.61 µg/m³

SO₂ – 0.55 µg/m³

CO – 156.17 µg/m³

NH₃ – 0.03 µg/m³

NO – 0 µg/m³

View Hourly Air Quality Forecast

Weather Alerts and Warnings for Ontario

Severe Future Likely

Extreme Heat Watch

Extreme Heat Watch issued March 14 at 5:51AM PDT until March 20 at 8:00PM PDT by NWS San Diego CA

Mar 16, 10:00 AM → Mar 20, 8:00 PM

WHAT: Dangerously hot conditions with temperatures 85 to 90 near
the coast, up to 105 inland.

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

WHEN: From Monday morning through Friday evening.

IMPACTS: Heat related illnesses increase significantly during
extreme heat events.

ADDITIONAL DETAILS: High temperatures next week will be 20 to
potentially 30 degrees above
normal for this time of year, where record breaking heat is likely.

+ Read More

Updated: Mar 14, 10:52 AM Source: NWS Alert

Moderate Expected Likely

Heat Advisory

Heat Advisory issued March 16 at 9:54PM PDT until March 20 at 8:00PM PDT by NWS San Diego CA

Mar 16, 9:54 PM → Mar 20, 8:00 PM

WHAT: Hot conditions with temperatures 80 to 90 degrees near the
coast and 95 to 102, locally up to 105 degrees inland. Overnight
lows will be in the 60s.

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

WHEN: Until 8 PM PDT Friday.

IMPACTS: Hot temperatures may cause heat illnesses. Increased
heat impacts due to long-duration early season heat wave.

ADDITIONAL DETAILS: High temperatures this week will be 20 to 30
degrees above normal for this time of year. Record breaking heat
is likely. Widespread Moderate to locally Major HeatRisk is
expected.

+ Read More

Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Do not leave young children and pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes. Take extra precautions when outside. Wear lightweight and loose fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke.

Updated: Mar 16, 11:37 PM Source: NWS Alert

Weather in Ontario, California

Ontario Weather Forecast Updated

Day

Night

Wind

UV Index

Precipitation

Air Quality in Ontario

Pollutant Concentrations:

Health Recommendations:

Weather Alerts and Warnings for Ontario

Extreme Heat Watch

Heat Advisory

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