SmogRank / United States / Illinois / Winthrop Harbor
Winthrop Harbor, month by month
Winthrop Harbor has a measured daily mean on 1,292 days since 1 January 2023. Its worst month was July 2026, at 83 US AQI (26.2 µg/m³), 196th of 2,784 cities on that month's world ranking. Its cleanest was May 2025, at 23 US AQI (4.2 µg/m³). 2025 averaged 42 US AQI (7.6 µg/m³), against 33 US AQI (6.0 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
3 months
| Month | Why |
|---|---|
| Nov 2025 | 12 of 30 days measured; a month needs 21. The others: 18 with under 18 hours of readings or readings that failed our checks. |
| Mar 2023 | 11 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive. |
| Feb 2023 | 3 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Winthrop Harbor's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| July 2026 | 8326.2 µg/m³ | 196thof 2,784 | Northern United States and Canada, July 2026 |
| June 2023 | 8225.5 µg/m³ | 168thof 1,603 | Eastern United States and Canada, June and July 2023 North-eastern United States, June 2023and 1 more |
| July 2025 | 6014.1 µg/m³ | 491stof 2,889 | North-eastern United States and Canada, 29 July to 9 August 2025 Northern United States, July 2025and 1 more |
| June 2025 | 5812.7 µg/m³ | 704thof 2,508 | Northern United States and Canada, May and June 2025 |
| August 2025 | 5712.1 µg/m³ | 748thof 2,901 | North-eastern United States and Canada, 29 July to 9 August 2025 |
| July 2023 | 5310.3 µg/m³ | 631stof 1,432 | Northern United States and Canada, July 2023 Eastern United States and Canada, June and July 2023 |
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.
Winthrop Harbor's worst days
| Day | US AQI | Episode |
|---|---|---|
| 16 Jul 2026 | 398274.0 µg/m³ | Northern United States and Canada, July 2026 |
| 27 Jun 2023 | 204129.0 µg/m³ | Eastern United States and Canada, June and July 2023 |
| 17 Jul 2026 | 202127.0 µg/m³ | Northern United States and Canada, July 2026 |
| 28 Jun 2023 | 191112.0 µg/m³ | Eastern United States and Canada, June and July 2023 |
| 31 Jul 2025 | 16677.5 µg/m³ | North-eastern United States and Canada, 29 July to 9 August 2025 |
| 29 Jun 2023 | 15865.0 µg/m³ | Eastern United States and Canada, June and July 2023 |
| 19 Jul 2026 | 13549.4 µg/m³ | Northern United States and Canada, July 2026 |
| 4 Jun 2025 | 12244.2 µg/m³ | Northern United States and Canada, May and June 2025 |
| 20 Jul 2026 | 12143.5 µg/m³ | Northern United States and Canada, July 2026 |
| 3 Aug 2025 | 11741.8 µg/m³ | North-eastern United States and Canada, 29 July to 9 August 2025 |
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, Winthrop Harbor, 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/winthrop-harbor/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.
Winthrop Harbor now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-12 20:07 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).