SmogRank / United States / Montana / Havre

Havre, month by month

Havre, Montana has a measured daily mean on 1,134 days since 5 May 2023. Its worst month was May 2023, at 63 US AQI (15.4 µg/m³), 139th of 1,600 cities on that month's world ranking. Its cleanest was September 2026, at 13 US AQI (2.3 µg/m³). 2025 averaged 26 US AQI (4.7 µg/m³), against 25 US AQI (4.5 µg/m³) in 2024.

Every month since 2023

202626 so far274 days measured2,693rd of 2,793 in the world
Jan14#2,592Feb14#2,839Mar22#2,823Apr18#2,835May20#2,729Jun13#2,471Jul56#974Aug53#849Sep13#2,963Oct16#2,710
202526 for the year298 days measured2,574th of 2,681 in the world
Jan15#2,456Feb18#2,588Mar16#2,820Apr18#2,898May20 daysJun52#1,326Jul43#1,824Aug37#2,326Sep14 daysOct21 daysNov17 daysDec19#2,907
202425 for the year332 days measured2,005th of 2,097 in the world
Jan27#2,096Feb24#2,273Mar23#1,469Apr18#2,373May28#2,272Jun17#2,488Jul15 daysAug51#845Sep27#1,814Oct18#1,989Nov18#2,554Dec18#2,534
2023too few days for a mean (a year needs 256)230 days measured
JanFebMarAprMay63#139Jun42#1,166Jul62#140Aug55#451Sep62#176Oct19#1,960Nov21#2,146Dec16#2,212
Each square is a month's mean PM2.5 in US AQI from Havre'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 Havre 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

5 months
MonthWhy
Nov 202517 of 30 days measured; a month needs 21. The others: 1 with no readings from the monitor, 10 with readings for part of the day (a day needs 18 hours), 2 with under 18 hours of readings or readings that failed our checks.
Oct 202521 of 31 days measured; a month needs 22. The others: 6 with no readings from the monitor, 4 with readings for part of the day (a day needs 18 hours).
Sep 202514 of 30 days measured; a month needs 21. The others: 15 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours).
May 202520 of 31 days measured; a month needs 22. The others: 7 with no readings from the monitor, 4 with readings for part of the day (a day needs 18 hours).
Jul 202415 of 31 days measured; a month needs 22. The others: 9 with no readings from the monitor, 7 with readings for part of the day (a day needs 18 hours).

A day counts once 18 hours of it are measured; a month needs 70% of its days.

Havre's worst months

MonthUS AQIDays measuredWorld rankEpisode
May 2023 6315.4 µg/m³27 of 31139thof 1,600North-western United States and Canada, May 2023
North-western Canada and United States, May 2023and 1 more
July 2023 6215.1 µg/m³26 of 31140thof 1,432United States and Canada, July 2023
North-western Canada and United States, July 2023
September 2023 6215.0 µg/m³30 of 30176thof 2,176Northern United States and Canada, August and September 2023
North-western Canada and United States, September 2023
July 2026 5611.6 µg/m³25 of 31974thof 2,784North-western United States and Canada, July and August 2026
August 2023 5511.0 µg/m³31 of 31451stof 1,980Northern United States and Canada, August and September 2023
North-western United States and Canada, August 2023
August 2026 5310.2 µg/m³31 of 31849thof 2,896North-western United States and Canada, July and August 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.

Havre's worst days

DayUS AQIEpisode
4 Sept 2023 211136.0 µg/m³Northern United States and Canada, August and September 2023
21 May 2023 206131.0 µg/m³North-western United States and Canada, May 2023
5 Sept 2023 184102.0 µg/m³Northern United States and Canada, August and September 2023
16 Jul 2023 17386.2 µg/m³United States and Canada, July 2023
11 Jun 2025 15865.1 µg/m³North-western Canada and United States, June 2025
2 Aug 2026 15662.7 µg/m³North-western United States and Canada, July and August 2026
20 May 2023 15561.3 µg/m³North-western United States and Canada, May 2023
15 Jul 2023 15460.4 µg/m³United States and Canada, July 2023
9 Aug 2025 13951.1 µg/m³Western Canada and United States, August 2025
17 May 2023 13147.5 µg/m³Northern United States and Canada, May 2023

Daily means, the highest since 5 May 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, Havre, Montana, United States, 5 May 2023 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/havre/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.

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

Updated 2026-10-12 22:07 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).