SmogRank / United States / California / Modesto
Modesto, month by month
Modesto has a measured daily mean on 1,301 days since 1 January 2023. Its worst month was January 2026, at 70 US AQI (19.5 µg/m³), 457th of 2,617 cities on that month's world ranking. Its cleanest was April 2026, at 20 US AQI (3.6 µg/m³). 2025 averaged 46 US AQI (8.3 µg/m³), against 48 US AQI (8.6 µg/m³) in 2024.
Every month since 2023
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
Months without a mean, and why
2 months
| Month | Why |
|---|---|
| Nov 2025 | 14 of 30 days measured; a month needs 21. The others: 16 with under 18 hours of readings or readings that failed our checks. |
| Dec 2024 | 20 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Modesto's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| January 2026 | 7019.5 µg/m³ | 457thof 2,617 | California, United States, 30 January to 6 February 2026 California, United States, 26 to 27 January 2026and 1 more |
| December 2023 | 7019.2 µg/m³ | 174thof 2,247 | Western United States and Mexico, December 2023 California and Oregon, United States, December 2023 |
| December 2025 | 6516.6 µg/m³ | 662ndof 3,006 | California, United States, December 2025 |
| January 2025 | 6416.0 µg/m³ | 440thof 2,474 | California, United States, January 2025 South-western United States and Mexico, December 2024 to January 2025 |
| November 2023 | 6214.8 µg/m³ | 153rdof 2,243 | – |
| February 2026 | 6114.7 µg/m³ | 795thof 2,866 | California, United States, 30 January to 6 February 2026 |
Monthly means over the days measured; finished months only. World rank: its place on that month's world ranking of every city with enough days. Each month opens that ranking.
Modesto's worst days
Daily means, the highest since 1 Jan 2023; the WHO's daily guideline is 15 µg/m³. Each date opens that day's world ranking, and each episode the bad-air spell it was part of.
Use this history
SmogRank, PM2.5 monthly and daily means, Modesto, United States, 1 Jan 2023 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/modesto/history (accessed 12 Oct 2026).
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.
Modesto now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 18:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index. Some low-cost readings: Sensor.Community, ODbL (data and licence). Some readings: Uzhydromet (Uzbekistan's Hydrometeorological Service); Department of Environment, Nepal; Vietnam's government monitors; Aurassure; Umhverfisstofnun (Environment Agency of Iceland); RMCAB (Secretaría Distrital de Ambiente, Bogotá); Love My Air (City and County of Denver), no reuse terms published (why we use them).