Salem — Seasonal Pollution Patterns
Month-by-month air quality patterns for Salem across 3 years of CPCB data. Based on CPCB station data, 2016–present.
Tamil Nadu · Live Salem AQI →
At a glance
Based on 3 years of CPCB monitoring across 1 stations, Salem averages AQI 73 annually, with a pronounced seasonal pattern classified as bimodal (two peaks). The worst month is April at AQI 91 (Satisfactory) and the cleanest is September at AQI 47 (Good) — a 44-point swing between them. Severe days (AQI > 400) make up 0% of the record while Good-or-Satisfactory days account for 87.1%.
The four seasons
Indian meteorological seasons: Winter (Dec–Feb), Summer (Mar–May), Monsoon (Jun–Sep), Post-monsoon (Oct–Nov).
Winter
AQI 83Summer
AQI 85Monsoon
AQI 57Post-monsoon
AQI 70Climograph — monthly averages and Poor+ days
Bars show the long-run AQI average per month. The overlay line counts days in Poor, Very Poor or Severe bands.
Year × month heatmap
One cell per year-month combination.
Each cell = monthly average AQI for that year-month combination. Row averages on the right, column averages at the bottom.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Avg |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2022 | — | — | — | — | — | — | — | — | 53 | 126 | 71 | 79 | 73 |
| 2023 | 87 | 97 | 78 | 87 | 76 | 91 | 65 | 64 | 47 | 73 | 78 | 93 | 77 |
| 2024 | 85 | 69 | 77 | 97 | 93 | 82 | — | 45 | 44 | 58 | 67 | 60 | 68 |
| Avg | 86 | 81 | 78 | 91 | 86 | 86 | 65 | 57 | 47 | 68 | 73 | 81 | — |
Winter in Salem
Winter (Dec–Jan–Feb) in Salem averages AQI 83 across 125 measured days — Satisfactory on the NAQI scale. 0% of those days fall in Very Poor or Severe; 82.4% are Good or Satisfactory. Year-on-year, winter improved by 20% in the most recent comparison. Winter in Salem is not the headline season, but shallow morning inversions can still produce short spikes. Salem's cleanest months lie elsewhere in the calendar, so the winter response is less about evacuation than about protecting sensitive groups on the worst individual days.
Diwali, stubble burning and the monsoon
Three India-specific signatures that shape the seasonal curve.
Diwali week impact
The 7-day window around Diwali averages AQI 113 (Moderate), versus 58 (Satisfactory) for the rest of October. 15 sampled days across the CPCB record.
Stubble-burning window (Oct 15 – Nov 15)
In-window severe-day share 0% vs 0% outside the window. The difference is a direct signal of upwind crop-residue transport.
Monsoon cleansing (Jul 15 – Sep 15)
Core monsoon window averages AQI 53 (Satisfactory), compared with an annual mean of 73.
Summer
Summer (Mar–Apr–May) in Salem averages AQI 85 across 64 measured days — Satisfactory on the NAQI scale. 0% of those days fall in Very Poor or Severe; 89.1% are Good or Satisfactory. Year-on-year, summer worsened by 16.7% in the most recent comparison. Summer air in Salem is shaped by a very different mix of forces. Rising temperatures drive deeper vertical mixing which dilutes local emissions, but pre-monsoon dust storms, wildfires and heat-accelerated ozone formation can all push AQI higher on individual days. Salem's summer mean of 85 is the lighter side of the year for outdoor activity, though hot afternoons can still irritate sensitive airways.
Monsoon
Monsoon (Jun–Jul–Aug–Sep) in Salem averages AQI 57 across 104 measured days — Satisfactory on the NAQI scale. 0% of those days fall in Very Poor or Severe; 96.2% are Good or Satisfactory. Year-on-year, monsoon improved by 13.3% in the most recent comparison. The Jul 15 – Sep 15 core monsoon window averages AQI 53, a 27.4% improvement on the annual mean of 73. Rain scrubs particulates out by wet deposition, and the deeper monsoon boundary layer disperses what remains vertically. Short-lived rebounds can happen between spells of rain, but the overall pattern is strongly favourable for outdoor activity. For anyone with asthma or heart conditions, monsoon is the easy-breathing stretch of the year in Salem.
Post-monsoon
Post-monsoon (Oct–Nov) in Salem averages AQI 70 across 101 measured days — Satisfactory on the NAQI scale. 0% of those days fall in Very Poor or Severe; 82.2% are Good or Satisfactory. Year-on-year, post-monsoon improved by 20.1% in the most recent comparison. Diwali and the three days either side of it average AQI 113 — 1.94× the normal October baseline of AQI 58 for Salem, a spike of 55 points. Post-monsoon in Salem is the handoff from clean monsoon air to the winter peak, and the transition is rarely gentle.
Month-by-month trajectories
How each month has moved across the 3-year CPCB record.
First year vs latest year
Annual and per-season comparison.
Across the 3-year CPCB record Salem is roughly stable overall — AQI moved from 73 in 2022 to 68 in 2024, a -6.8% change. No month shows a material worsening of 10% or more. No month shows a material improvement of 10% or more. Because Salem's seasonal shape is bimodal (two peaks), policy action that targets the April peak buys disproportionate relief — most city-wide annual averages are dragged upwards by the worst two or three months.
Daily calendar heatmap
Every measured day for the last 3 years. Expand for the full 3-year archive.
Month-by-month deep dive
Tap any month to expand.
Jan2023–2024Latest AQI 85-2%
Jan in Salem averages AQI 85 (Satisfactory) in the most recent year, having moved from 87 in 2023. Direction: stable (-2.3%).
Feb2023–2024Latest AQI 69-29%
Feb in Salem averages AQI 69 (Satisfactory) in the most recent year, having moved from 97 in 2023. Direction: improving (-28.9%).
Mar2023–2024Latest AQI 77-1%
Mar in Salem averages AQI 77 (Satisfactory) in the most recent year, having moved from 78 in 2023. Direction: stable (-1.3%).
Apr2023–2024Latest AQI 97+12%
Apr in Salem averages AQI 97 (Satisfactory) in the most recent year, having moved from 87 in 2023. Direction: worsening (+11.5%).
May2023–2024Latest AQI 93+22%
May in Salem averages AQI 93 (Satisfactory) in the most recent year, having moved from 76 in 2023. Direction: worsening (+22.4%).
Jun2023–2024Latest AQI 82-10%
Jun in Salem averages AQI 82 (Satisfactory) in the most recent year, having moved from 91 in 2023. Direction: stable (-9.9%).
Jul2023–2023Latest AQI 65+0%
Jul in Salem averages AQI 65 (Satisfactory) in the most recent year, having moved from 65 in 2023. Direction: stable (+0.0%).
Aug2023–2024Latest AQI 45-30%
Aug in Salem averages AQI 45 (Good) in the most recent year, having moved from 64 in 2023. Direction: improving (-29.7%).
Sep2022–2024Latest AQI 44-17%
Sep in Salem averages AQI 44 (Good) in the most recent year, having moved from 53 in 2022. Direction: improving (-17.0%).
Oct2022–2024Latest AQI 58-54%
Oct in Salem averages AQI 58 (Satisfactory) in the most recent year, having moved from 126 in 2022. Direction: improving (-54.0%).
Nov2022–2024Latest AQI 67-6%
Nov in Salem averages AQI 67 (Satisfactory) in the most recent year, having moved from 71 in 2022. Direction: stable (-5.6%).
Dec2022–2024Latest AQI 60-24%
Dec in Salem averages AQI 60 (Satisfactory) in the most recent year, having moved from 79 in 2022. Direction: improving (-24.1%).
Cities with similar (and opposite) seasonal profiles
Ranked by cosine similarity of 12-month AQI signatures across monitored Indian cities.
Similar seasonal profile
Cities whose 12-month AQI signature most closely matches Salem.
Opposite seasonal profile
Cities whose seasonal signature least resembles Salem.
What to do with this information
If you are choosing when to visit Salem or plan outdoor events — marathons, weddings, school sports, outdoor festivals — the CPCB record says September and the two adjacent months are the lowest-risk window. Daily variability still matters; check the live AQI page before committing on any specific date. Sensitive groups should treat April in Salem as an indoor-air-priority month: close windows on high-AQI evenings, run a purifier with a HEPA filter rated for your room size, and reserve outdoor exercise for clear-weather mornings. On days above AQI 300, even healthy adults benefit from well-fitted N95 or KN95 masks for outdoor commutes.
Frequently asked questions
Which is the most polluted month in Salem?
April is the most polluted month in Salem on average, with a long-run AQI of 91 — firmly in the Satisfactory band. This is drawn from 1 CPCB monitoring stations across 3 years of daily readings. Through April, residents should expect elevated PM2.5 and PM10, reduced visibility on cooler mornings, and strong recommendations from doctors to limit outdoor exertion, wear well-fitted N95 masks, and run indoor purifiers through evening and overnight hours when pollutant accumulation typically peaks.
What is the cleanest month to visit Salem?
September is the cleanest month of the year in Salem, averaging AQI 47 in the Good band. The months immediately before and after also tend to sit well below the annual mean of 73, so a visit window centred on September is the safest choice for outdoor sightseeing, marathons, school trips and wedding events. Mornings are usually the crispest time to head out; pollution tends to creep up slightly during the evening commute even in the cleanest months. Always cross-check the day-of live AQI before any high-exertion outdoor plan.
Why does Salem's air spike in April?
Salem has a bimodal pattern — two peaks in the year separated by cleaner months. The headline April reflects a mix of seasonal dust, emissions trapping and regional transport rather than one dominant driver.
How bad is Diwali air quality in Salem?
Across the CPCB record, the week around Diwali in Salem averages AQI 113 — 1.94× the normal October baseline of AQI 58, a spike of 55 AQI points. Firework particulates combine with a cooler, more stagnant late-October atmosphere to produce some of the worst air-quality days of the entire year. Sensitive groups should treat Diwali eve and the two days after as peak-alert days: stay indoors, close windows by evening, run purifiers on high, and reserve any outdoor celebrations for daytime hours when mixing is strongest.
Does the monsoon actually clean Salem's air?
Yes — meaningfully. Salem's core monsoon window (Jul 15 – Sep 15) averages AQI 53, a 27.4% improvement on the annual mean of 73. Rain removes airborne particulates by wet deposition, and the deeper monsoon boundary layer disperses what remains vertically. Across 104 measured monsoon days we see 96.2% in the Good-or-Satisfactory band.
Is Salem's worst season getting worse or better year-on-year?
Between 2022 and 2024, Salem's annual average AQI moved from 73 to 68 — a change of -6.8%. In the most recent year-on-year comparison, the winter season specifically improved by 20%. The long-run direction is roughly stable — underlying growth in emissions is being offset by cleaner technology or weather variability.
Which months are safest to visit Salem?
September is the single best month at AQI 47. Based on the 12-month averages, the three cleanest months in Salem are September (AQI 47), August (AQI 57), July (AQI 65). These are the safest choices for outdoor itineraries, long walks, open-air concerts and day-trips. Sensitive groups can treat these months as near-normal activity windows but should still check live AQI for the specific date. Avoid planning outdoor-heavy trips in April, when the baseline jumps into Satisfactory territory.
How does Salem's seasonal pattern compare to other Indian cities?
Salem is classified as bimodal (two peaks). Based on a 12-month cosine-similarity index computed across all monitored Indian cities, the city whose seasonal signature most closely resembles Salem's is Pāli (Rajasthan), with its own worst month in May. Cities with similar signatures often respond to similar policy levers — if a neighbouring peer has demonstrated improvements through specific interventions (construction-dust controls, bus electrification, brick-kiln regulation), they are likely candidates for Salem too. The peer-city panel on this page lists the closest four additional matches.