SmogRank / India / Bihar / Siwān

Siwān, month by month

Siwān has a measured daily mean on 303 days since 21 February 2025. Its worst month was August 2026, at 128 US AQI (46.3 µg/m³), 28th of 2,896 cities on that month's world ranking. Its cleanest was September 2025, at 74 US AQI (21.5 µg/m³).

Every month since 2025

2026too few days for a mean (a year needs 200)149 days measured
Jan20 daysFeb97#208Mar14 daysApr96#196May16 daysJun8 daysJul8 daysAug128#28Sep13 daysOct5 days
2025too few days for a mean (a year needs 256)154 days measured
JanFeb4 daysMar13 daysApr15 daysMay6 daysJun8 daysJul8 daysAug19 daysSep74#180Oct21 daysNov14 daysDec21 days
Each square is a month's mean PM2.5 in US AQI from Siwān'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 Siwān marked; each year, the year's.
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

17 months
MonthWhy
Oct 20265 of 12 days measured; a month needs 9. The others: 6 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours).
Sep 202613 of 30 days measured; a month needs 21. The others: 10 with no readings from the monitor, 7 with readings for part of the day (a day needs 18 hours).
Jul 20268 of 31 days measured; a month needs 22. The others: 23 with under 18 hours of readings or readings that failed our checks.
Jun 20268 of 30 days measured; a month needs 21. The others: 22 with under 18 hours of readings or readings that failed our checks.
May 202616 of 31 days measured; a month needs 22. The others: 15 with under 18 hours of readings or readings that failed our checks.
Mar 202614 of 31 days measured; a month needs 22. The others: 17 with under 18 hours of readings or readings that failed our checks.
Jan 202620 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks.
Dec 202521 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks.
Nov 202514 of 30 days measured; a month needs 21. The others: 16 with under 18 hours of readings or readings that failed our checks.
Oct 202521 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks.
Aug 202519 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks.
Jul 20258 of 31 days measured; a month needs 22. The others: 23 with under 18 hours of readings or readings that failed our checks.
Jun 20258 of 30 days measured; a month needs 21. The others: 22 with under 18 hours of readings or readings that failed our checks.
May 20256 of 31 days measured; a month needs 22. The others: 25 with under 18 hours of readings or readings that failed our checks.
Apr 202515 of 30 days measured; a month needs 21. The others: 15 with under 18 hours of readings or readings that failed our checks.
Mar 202513 of 31 days measured; a month needs 22. The others: 18 with under 18 hours of readings or readings that failed our checks.
Feb 20254 of 28 days measured; a month needs 20. The others: 4 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.

Siwān's worst months

MonthUS AQIDays measuredWorld rankEpisode
August 2026 12846.3 µg/m³23 of 3128thof 2,896Bihar, Odisha and Uttar Pradesh, India, August 2026
February 2026 9733.8 µg/m³21 of 28208thof 2,866–
April 2026 9633.0 µg/m³21 of 30196thof 2,941–
September 2025 7421.5 µg/m³25 of 30180thof 3,104–

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.

Siwān's worst days

DayUS AQIEpisode
19 May 2025 298223.0 µg/m³–
20 Apr 2025 270195.0 µg/m³–
20 May 2025 239164.0 µg/m³–
19 Apr 2025 226151.0 µg/m³–
26 Mar 2025 221146.0 µg/m³Northern India, March and April 2025
12 Apr 2025 220145.0 µg/m³–
25 Mar 2025 219144.0 µg/m³Northern India, March and April 2025
13 Apr 2025 213138.0 µg/m³–
21 Mar 2025 196119.0 µg/m³–
20 Oct 2025 186105.0 µg/m³India and Pakistan, October 2025

Daily means, the highest since 21 Feb 2025; 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, Siwān, India, 21 Feb 2025 – 7 Oct 2026. Monitor data from CPCB via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/in/siwan/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.

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

Updated 2026-10-12 19:07 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).