SmogRank / United States / California

Air quality in Modesto

California, United States. PM2.5 from 1 reference monitor, updated hourly.

13.9 µg/m³
Moderate

Latest hour (08:00 UTC), 0.9× the WHO 24-hour guideline.

Rank

24 h
–
not enough data
7 days
–
not enough data
30 days
#1,738
of 2,331 · 5.1 µg/m³
Year
#1,429
of 2,173 · 8.0 µg/m³

Why it ranks here

Seasonal. Over the past year its worst months were January, December, averaging up to 19.5 µg/m³ against 3.6 in its cleanest month. Seasonal peaks usually come from heating, crop burning, fire or dust seasons.

Based on Modesto's own measurements; causes are the usual kinds for a pattern like this, not a confirmed source.

Last 4 days, hour by hour

15302026-10-01 00:00 UTC: 11.0 µg/m³2026-10-01 01:00 UTC: 10.6 µg/m³2026-10-01 02:00 UTC: 8.3 µg/m³2026-10-01 03:00 UTC: 15.4 µg/m³2026-10-01 04:00 UTC: 16.6 µg/m³2026-10-01 05:00 UTC: 16.0 µg/m³2026-10-01 06:00 UTC: 12.0 µg/m³2026-10-01 08:00 UTC: 13.9 µg/m³Sep 28Sep 29Sep 30Oct 1

Times in UTC. Dashed line: WHO 24-hour guideline (15 µg/m³).

Every day for a year

SepNovDecJanFebMarAprMayJunJulAugSepMonWedFri2025-09-29: no data2025-09-30: 4.8 µg/m³2025-10-01: 4.1 µg/m³2025-10-02: 4.2 µg/m³2025-10-03: 7.1 µg/m³2025-10-04: 7.5 µg/m³2025-10-05: 7.1 µg/m³2025-10-06: 7.3 µg/m³2025-10-07: 7.8 µg/m³2025-10-08: 9.1 µg/m³2025-10-09: 7.5 µg/m³2025-10-10: 5.8 µg/m³2025-10-11: 3.6 µg/m³2025-10-12: 4.7 µg/m³2025-10-13: 7.6 µg/m³2025-10-14: 3.5 µg/m³2025-10-15: 6.3 µg/m³2025-10-16: 6.5 µg/m³2025-10-17: 16.6 µg/m³2025-10-18: 26.1 µg/m³2025-10-19: 19.8 µg/m³2025-10-20: 7.8 µg/m³2025-10-21: 10.5 µg/m³2025-10-22: 10.5 µg/m³2025-10-23: 12.9 µg/m³2025-10-24: 15.9 µg/m³2025-10-25: 6.8 µg/m³2025-10-26: 6.1 µg/m³2025-10-27: 5.2 µg/m³2025-10-28: 11.0 µg/m³2025-10-29: 14.2 µg/m³2025-10-30: 14.7 µg/m³2025-10-31: 14.2 µg/m³2025-11-01: 16.5 µg/m³2025-11-02: 14.6 µg/m³2025-11-03: 14.9 µg/m³2025-11-04: no data2025-11-05: no data2025-11-06: no data2025-11-07: no data2025-11-08: 7.2 µg/m³2025-11-09: 13.1 µg/m³2025-11-10: 13.8 µg/m³2025-11-11: 25.9 µg/m³2025-11-12: 12.5 µg/m³2025-11-13: 6.2 µg/m³2025-11-14: no data2025-11-15: no data2025-11-16: no data2025-11-17: no data2025-11-18: no data2025-11-19: no data2025-11-20: no data2025-11-21: 9.4 µg/m³2025-11-22: 15.0 µg/m³2025-11-23: 15.2 µg/m³2025-11-24: 14.6 µg/m³2025-11-25: 15.4 µg/m³2025-11-26: no data2025-11-27: no data2025-11-28: no data2025-11-29: no data2025-11-30: no data2025-12-01: 25.2 µg/m³2025-12-02: 24.5 µg/m³2025-12-03: 20.9 µg/m³2025-12-04: 26.2 µg/m³2025-12-05: 24.4 µg/m³2025-12-06: 34.1 µg/m³2025-12-07: 26.7 µg/m³2025-12-08: no data2025-12-09: no data2025-12-10: 19.2 µg/m³2025-12-11: 20.4 µg/m³2025-12-12: 14.8 µg/m³2025-12-13: 16.5 µg/m³2025-12-14: 22.8 µg/m³2025-12-15: 13.3 µg/m³2025-12-16: 13.9 µg/m³2025-12-17: 20.9 µg/m³2025-12-18: 15.7 µg/m³2025-12-19: 16.0 µg/m³2025-12-20: 20.6 µg/m³2025-12-21: 12.6 µg/m³2025-12-22: 6.3 µg/m³2025-12-23: 11.8 µg/m³2025-12-24: 2.9 µg/m³2025-12-25: 2.9 µg/m³2025-12-26: 3.4 µg/m³2025-12-27: 7.4 µg/m³2025-12-28: 9.8 µg/m³2025-12-29: 12.0 µg/m³2025-12-30: 15.5 µg/m³2025-12-31: 21.1 µg/m³2026-01-01: 7.6 µg/m³2026-01-02: 5.5 µg/m³2026-01-03: 3.9 µg/m³2026-01-04: 2.9 µg/m³2026-01-05: 3.9 µg/m³2026-01-06: 5.0 µg/m³2026-01-07: 5.2 µg/m³2026-01-08: 4.1 µg/m³2026-01-09: 11.6 µg/m³2026-01-10: 16.8 µg/m³2026-01-11: 28.5 µg/m³2026-01-12: 22.9 µg/m³2026-01-13: 33.9 µg/m³2026-01-14: 32.6 µg/m³2026-01-15: 33.8 µg/m³2026-01-16: 37.1 µg/m³2026-01-17: 28.7 µg/m³2026-01-18: 24.2 µg/m³2026-01-19: 18.8 µg/m³2026-01-20: 16.5 µg/m³2026-01-21: 16.4 µg/m³2026-01-22: 22.5 µg/m³2026-01-23: 22.6 µg/m³2026-01-24: 20.1 µg/m³2026-01-25: 21.6 µg/m³2026-01-26: 27.5 µg/m³2026-01-27: 28.4 µg/m³2026-01-28: 21.2 µg/m³2026-01-29: 17.2 µg/m³2026-01-30: 28.5 µg/m³2026-01-31: 35.9 µg/m³2026-02-01: 28.3 µg/m³2026-02-02: 18.3 µg/m³2026-02-03: 35.5 µg/m³2026-02-04: 36.9 µg/m³2026-02-05: 35.9 µg/m³2026-02-06: 37.3 µg/m³2026-02-07: 20.5 µg/m³2026-02-08: 16.5 µg/m³2026-02-09: 6.2 µg/m³2026-02-10: 18.0 µg/m³2026-02-11: 7.8 µg/m³2026-02-12: 7.5 µg/m³2026-02-13: 10.3 µg/m³2026-02-14: 13.8 µg/m³2026-02-15: 6.9 µg/m³2026-02-16: 5.7 µg/m³2026-02-17: 5.5 µg/m³2026-02-18: 6.0 µg/m³2026-02-19: 6.3 µg/m³2026-02-20: 8.5 µg/m³2026-02-21: 11.4 µg/m³2026-02-22: 11.3 µg/m³2026-02-23: 10.4 µg/m³2026-02-24: 15.4 µg/m³2026-02-25: 9.1 µg/m³2026-02-26: 5.1 µg/m³2026-02-27: 6.4 µg/m³2026-02-28: 11.6 µg/m³2026-03-01: 5.0 µg/m³2026-03-02: 5.1 µg/m³2026-03-03: 5.6 µg/m³2026-03-04: 5.3 µg/m³2026-03-05: 4.9 µg/m³2026-03-06: 6.6 µg/m³2026-03-07: 10.6 µg/m³2026-03-08: 10.3 µg/m³2026-03-09: 12.2 µg/m³2026-03-10: 11.5 µg/m³2026-03-11: 8.5 µg/m³2026-03-12: 9.9 µg/m³2026-03-13: 12.0 µg/m³2026-03-14: 9.1 µg/m³2026-03-15: 6.5 µg/m³2026-03-16: 10.8 µg/m³2026-03-17: 15.7 µg/m³2026-03-18: 18.1 µg/m³2026-03-19: 14.5 µg/m³2026-03-20: 11.5 µg/m³2026-03-21: 13.8 µg/m³2026-03-22: 8.8 µg/m³2026-03-23: 7.5 µg/m³2026-03-24: 4.0 µg/m³2026-03-25: 3.6 µg/m³2026-03-26: 5.7 µg/m³2026-03-27: 4.4 µg/m³2026-03-28: 8.1 µg/m³2026-03-29: 7.4 µg/m³2026-03-30: 11.1 µg/m³2026-03-31: 8.3 µg/m³2026-04-01: 4.6 µg/m³2026-04-02: 2.0 µg/m³2026-04-03: 3.0 µg/m³2026-04-04: 6.7 µg/m³2026-04-05: 6.4 µg/m³2026-04-06: 5.3 µg/m³2026-04-07: 5.3 µg/m³2026-04-08: 3.6 µg/m³2026-04-09: 3.0 µg/m³2026-04-10: 2.1 µg/m³2026-04-11: 1.3 µg/m³2026-04-12: 2.1 µg/m³2026-04-13: 1.9 µg/m³2026-04-14: 2.8 µg/m³2026-04-15: 2.2 µg/m³2026-04-16: 1.8 µg/m³2026-04-17: 2.2 µg/m³2026-04-18: 3.4 µg/m³2026-04-19: 5.8 µg/m³2026-04-20: 2.6 µg/m³2026-04-21: 1.4 µg/m³2026-04-22: 2.1 µg/m³2026-04-23: 2.1 µg/m³2026-04-24: 3.7 µg/m³2026-04-25: 5.7 µg/m³2026-04-26: 4.0 µg/m³2026-04-27: 4.8 µg/m³2026-04-28: 5.3 µg/m³2026-04-29: 4.7 µg/m³2026-04-30: 5.2 µg/m³2026-05-01: 6.6 µg/m³2026-05-02: 5.8 µg/m³2026-05-03: 2.3 µg/m³2026-05-04: 1.0 µg/m³2026-05-05: 1.7 µg/m³2026-05-06: 3.7 µg/m³2026-05-07: 4.8 µg/m³2026-05-08: 4.9 µg/m³2026-05-09: 7.3 µg/m³2026-05-10: 3.7 µg/m³2026-05-11: 6.3 µg/m³2026-05-12: 5.5 µg/m³2026-05-13: 3.5 µg/m³2026-05-14: 3.7 µg/m³2026-05-15: 6.1 µg/m³2026-05-16: 6.5 µg/m³2026-05-17: 4.9 µg/m³2026-05-18: 0.7 µg/m³2026-05-19: 2.1 µg/m³2026-05-20: 4.3 µg/m³2026-05-21: 4.9 µg/m³2026-05-22: 6.0 µg/m³2026-05-23: 5.2 µg/m³2026-05-24: 3.2 µg/m³2026-05-25: 2.4 µg/m³2026-05-26: 3.0 µg/m³2026-05-27: 4.3 µg/m³2026-05-28: 3.5 µg/m³2026-05-29: 2.9 µg/m³2026-05-30: 2.4 µg/m³2026-05-31: 3.8 µg/m³2026-06-01: 4.8 µg/m³2026-06-02: 8.3 µg/m³2026-06-03: 6.9 µg/m³2026-06-04: 4.5 µg/m³2026-06-05: 8.4 µg/m³2026-06-06: 4.2 µg/m³2026-06-07: 5.8 µg/m³2026-06-08: 5.0 µg/m³2026-06-09: 1.7 µg/m³2026-06-10: 2.8 µg/m³2026-06-11: 4.3 µg/m³2026-06-12: 9.5 µg/m³2026-06-13: 5.5 µg/m³2026-06-14: 5.8 µg/m³2026-06-15: 6.0 µg/m³2026-06-16: 5.4 µg/m³2026-06-17: 4.5 µg/m³2026-06-18: 3.6 µg/m³2026-06-19: 2.9 µg/m³2026-06-20: 3.1 µg/m³2026-06-21: 2.9 µg/m³2026-06-22: 6.4 µg/m³2026-06-23: 5.4 µg/m³2026-06-24: 4.3 µg/m³2026-06-25: 6.4 µg/m³2026-06-26: 4.4 µg/m³2026-06-27: 1.1 µg/m³2026-06-28: 3.4 µg/m³2026-06-29: 3.9 µg/m³2026-06-30: 6.6 µg/m³2026-07-01: 8.9 µg/m³2026-07-02: 9.8 µg/m³2026-07-03: 7.5 µg/m³2026-07-04: 12.9 µg/m³2026-07-05: 7.9 µg/m³2026-07-06: 3.6 µg/m³2026-07-07: 4.9 µg/m³2026-07-08: 4.9 µg/m³2026-07-09: 6.0 µg/m³2026-07-10: 7.1 µg/m³2026-07-11: 2.4 µg/m³2026-07-12: 3.6 µg/m³2026-07-13: 6.9 µg/m³2026-07-14: 5.2 µg/m³2026-07-15: 4.5 µg/m³2026-07-16: 4.4 µg/m³2026-07-17: 5.0 µg/m³2026-07-18: 5.0 µg/m³2026-07-19: 3.3 µg/m³2026-07-20: 2.9 µg/m³2026-07-21: 3.1 µg/m³2026-07-22: 2.9 µg/m³2026-07-23: 2.8 µg/m³2026-07-24: 4.2 µg/m³2026-07-25: 4.9 µg/m³2026-07-26: 2.9 µg/m³2026-07-27: 3.9 µg/m³2026-07-28: 5.7 µg/m³2026-07-29: 4.4 µg/m³2026-07-30: 4.0 µg/m³2026-07-31: 7.3 µg/m³2026-08-01: 8.0 µg/m³2026-08-02: 9.4 µg/m³2026-08-03: 10.0 µg/m³2026-08-04: 9.4 µg/m³2026-08-05: 8.7 µg/m³2026-08-06: 5.9 µg/m³2026-08-07: 6.7 µg/m³2026-08-08: 6.7 µg/m³2026-08-09: 7.6 µg/m³2026-08-10: 10.0 µg/m³2026-08-11: 11.3 µg/m³2026-08-12: 8.1 µg/m³2026-08-13: 5.2 µg/m³2026-08-14: 2.9 µg/m³2026-08-15: 3.4 µg/m³2026-08-16: 3.8 µg/m³2026-08-17: 4.5 µg/m³2026-08-18: 5.6 µg/m³2026-08-19: 9.2 µg/m³2026-08-20: 5.4 µg/m³2026-08-21: 3.2 µg/m³2026-08-22: 2.2 µg/m³2026-08-23: 2.9 µg/m³2026-08-24: 4.5 µg/m³2026-08-25: 4.0 µg/m³2026-08-26: 1.7 µg/m³2026-08-27: 6.1 µg/m³2026-08-28: 5.1 µg/m³2026-08-29: 2.3 µg/m³2026-08-30: 5.1 µg/m³2026-08-31: 4.8 µg/m³2026-09-01: 5.0 µg/m³2026-09-02: 2.7 µg/m³2026-09-03: 2.0 µg/m³2026-09-04: 2.7 µg/m³2026-09-05: 4.1 µg/m³2026-09-06: 2.0 µg/m³2026-09-07: 3.4 µg/m³2026-09-08: 4.6 µg/m³2026-09-09: 5.1 µg/m³2026-09-10: 4.4 µg/m³2026-09-11: 4.4 µg/m³2026-09-12: 4.9 µg/m³2026-09-13: 4.4 µg/m³2026-09-14: 5.0 µg/m³2026-09-15: 7.6 µg/m³2026-09-16: 7.7 µg/m³2026-09-17: 5.8 µg/m³2026-09-18: 5.9 µg/m³2026-09-19: 6.5 µg/m³2026-09-20: 5.1 µg/m³2026-09-21: 4.3 µg/m³2026-09-22: no data2026-09-23: no data2026-09-24: no data2026-09-25: no data2026-09-26: 5.6 µg/m³2026-09-27: 7.3 µg/m³2026-09-28: 8.8 µg/m³2026-09-29: 9.2 µg/m³2026-09-30: no data
Good 0–9.0Moderate 9.1+Unhealthy for sensitive groups 35.5+Unhealthy 55.5+Very unhealthy 125.5+Hazardous 225.5+No data

59 of 342 measured days were over the WHO 24-hour guideline.

Daily world rank

#1#2328OctNovDecJanFebMarAprMayJunJulAugSep

Rank on each day's board (1 = most polluted city that day).

2026 against 2025, month by month

15Jan 2025: 16.0 µg/m³Jan 2026: 19.5 µg/m³JanFeb 2025: 7.0 µg/m³Feb 2026: 14.7 µg/m³FebMar 2025: 4.9 µg/m³Mar 2026: 8.9 µg/m³MarApr 2025: 5.7 µg/m³Apr 2026: 3.6 µg/m³AprMay 2025: 5.4 µg/m³May 2026: 4.1 µg/m³MayJun 2025: 6.1 µg/m³Jun 2026: 4.9 µg/m³JunJul 2025: 5.5 µg/m³Jul 2026: 5.3 µg/m³JulAug 2025: 5.4 µg/m³Aug 2026: 5.9 µg/m³AugSep 2025: 6.8 µg/m³Sep 2026: 5.1 µg/m³SepOct 2025: 9.4 µg/m³OctNov 2025: 13.9 µg/m³NovDec 2025: 16.6 µg/m³Dec

Faded bars: 2025. A month shows once it has 10 measured days.

This week against past years

This weekThis week: 7.7 µg/m³7.72025no data20242024: 9.2 µg/m³9.220232023: 7.8 µg/m³7.8

Mean PM2.5 for 24 Sept to 30 Sept in each year. Dashed line: WHO 24-hour guideline.

Monitors

StationOperatorType
Modesto - 14th StreeUS Public DomainAirNowReference
VIP-f5c4CC BY 4.0SJVAir.comLow-cost

The city's value is the median of its reference monitors each hour; low-cost sensors are listed but not counted when reference monitors exist. Data via OpenAQ; licences as listed. How we rank. Embed this on your site.

Other cities in United States

Calexico 23.0Jurupa Valley 12.9Riverside 12.3Little Rock 12.2Hanford 11.9Oceanside 11.8Laredo 11.4Shreveport 11.0Wake Forest 11.0Corcoran 11.0Fontana 11.0West Memphis 10.9

30-day averages, µg/m³. All of United States →

Updated 2026-10-01 09:07 UTC. Values are PM2.5 in µg/m³ (fine particles), the median of each city's monitors.