Modesto Air Quality in 2025: Pollution Patterns
How air quality behaves in Modesto: the latest measured AQI, which pollutants dominate, seasonal patterns, and the local drivers of pollution.
Current Air Quality
Air quality is satisfactory, and air pollution poses little or no risk.
Modesto Air Quality in 2025
This page covers what shapes air quality in Modesto over the course of a year: the pollutants that dominate locally, how conditions typically shift between seasons, and the local emission sources behind them. Measured 2025 annual statistics are published by EPA's Air Quality System, not here, so the AQI figure below is the latest observation available when this page was published.
View Current Modesto Air Quality →Latest Measured Reading for Modesto
The most recent EPA AirNow observation for the Modesto reporting area puts Modesto's AQI at 46 (Good), with fine particulate matter (PM2.5) as the dominant pollutant — typical for the West Coast region. Observed 3:00 AM PDT on August 9, 2026. Reported by San Joaquin Valley Unified APCD.
This is a single observation captured when the page was published, not a 2025 average. For measured annual and monthly statistics, use the EPA's Air Quality System reports.
How Modesto Air Quality Shifts Through the Year
Mar–May: Usually Modesto's cleanest stretch. Mild temperatures and better atmospheric mixing keep both ozone and particulates down.
Jun–Aug: Heat and sunlight drive higher ozone and, in the West, wildfire-smoke episodes. Afternoons are typically the worst time to be outside.
Sep–Nov: Air quality generally improves as temperatures drop, though early fall can still carry wildfire smoke in the West Coast region.
Dec–Feb: Cold-air temperature inversions can trap PM2.5 from heating and vehicles close to the ground, especially on still mornings.
Seasonal patterns above describe how pollution typically behaves in this region. They are not measured 2025 averages for Modesto.
Is It Safe to Exercise Outside in Modesto?
With Modesto's AQI at 46 (Good), outdoor exercise is generally safe for most people. Conditions are good for running, cycling, and outdoor sports at any time of day.
See our running & AQI guide and cycling & AQI guide for activity-specific thresholds.
What's Causing Modesto's Air Pollution?
In Modesto, the leading pollutant is fine particulate matter (PM2.5). As part of the West Coast region, the main drivers of air pollution here are:
- •Vehicle emissions from heavily trafficked freeways and urban corridors
- •Seasonal wildfire smoke drifting in from forest fires across the West
- •Port, shipping, and warehouse logistics activity
- •Agricultural operations and dust in nearby valleys
Dig deeper: Modesto PM2.5 levels · Modesto ozone levels
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PM2.5 Levels
Fine particulate matter data →
Ozone Levels
Ground-level ozone data →
Seasonal Guides
Air quality by season →
Health Effects
Learn about air pollution impacts →
Frequently Asked Questions About Modesto Air Quality
What is the current air quality in Modesto?
The current Air Quality Index (AQI) in Modesto, CA is 46, which is considered good.
Is it safe to exercise outdoors in Modesto?
Yes, with an AQI of 46, outdoor exercise is safe for everyone in Modesto.
When is the best time of year to visit Modesto for good air quality?
Spring and early fall typically offer the best air quality in Modesto. Summer months may have elevated ozone levels, while winter can see higher PM2.5 from temperature inversions.
What causes air pollution in Modesto?
Air pollution in Modesto can come from vehicle emissions, industrial activity, construction, wildfires, and weather patterns. Local geography and seasonal factors also play a significant role.
Explore More Air Quality Data
Improve Indoor Air Quality
Even with good outdoor air in Modesto, indoor PM2.5, dust and allergens build up. A True-HEPA purifier keeps a bedroom or office consistently clean.
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