SmogRank / United States / Florida / Four Corners

Four Corners, month by month

Four Corners has a measured daily mean on 650 days since 10 December 2024. Its worst month was July 2026, at 51 US AQI (9.1 µg/m³), 1,581st of 2,784 cities on that month's world ranking. Its cleanest was September 2025, at 24 US AQI (4.3 µg/m³).

Every month since 2024

202636 so far275 days measured2,401st of 2,793 in the world
Jan33#2,149Feb35#2,376Mar38#2,404Apr34#2,144May36#1,810Jun36#1,735Jul51#1,581Aug37#2,249Sep26#2,483Oct22#2,539
202537 for the year354 days measured2,220th of 2,681 in the world
Jan35#1,911Feb38#1,865Mar47#1,853Apr42#1,890May41#1,527Jun43#1,868Jul43#1,850Aug29#2,649Sep24#2,864Oct28#2,039Nov36#2,076Dec32#2,530
2024too few days for a mean (a year needs 257)21 days measured
JanFebMarAprMayJunJulAugSepOctNovDec21 days
Each square is a month's mean PM2.5 in US AQI from Four Corners's measured days, with its place on that month's world ranking under it. A month has a mean once 70% of its days are measured, the rule the monthly rankings use; under that, the square gives the days measured. Each square opens that month's ranking with Four Corners marked; each year, the year's. A dashed square is the running month, so far.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

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

1 month
MonthWhy
Dec 202421 of 31 days measured; a month needs 22. The others: 1 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.

Four Corners's worst months

MonthUS AQIDays measuredWorld rank
July 2026 519.1 µg/m³29 of 311,581stof 2,784
March 2025 478.5 µg/m³31 of 311,853rdof 2,862
June 2025 437.8 µg/m³30 of 301,868thof 2,508
July 2025 437.7 µg/m³31 of 311,850thof 2,889
April 2025 427.5 µg/m³29 of 301,890thof 2,951
May 2025 417.3 µg/m³31 of 311,527thof 2,826

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.

Four Corners's worst days

DayUS AQI
8 Mar 2025 9030.3 µg/m³
5 Jun 2025 7220.3 µg/m³
25 Jul 2025 6918.5 µg/m³
26 Jul 2025 6818.4 µg/m³
9 Jul 2026 6818.2 µg/m³
10 Jul 2026 6616.9 µg/m³
7 Mar 2025 6416.0 µg/m³
9 Jun 2025 6315.6 µg/m³
1 Jan 2026 6315.5 µg/m³
27 Jul 2025 6114.4 µg/m³

Daily means, the highest since 10 Dec 2024; 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, Four Corners, United States, 10 Dec 2024 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/four-corners/history (accessed 12 Oct 2026).

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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.

Four Corners now: the last 24 hours, its ranks today and the last 12 months day by day.

Updated 2026-10-12 23:07 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).