Gangtok — Seasonal Pollution Patterns
Month-by-month air quality patterns for Gangtok across 3 years of CPCB data. Based on CPCB station data, 2016–present.
Sikkim · Live Gangtok AQI →
At a glance
Based on 3 years of CPCB monitoring across 1 stations, Gangtok averages AQI 50 annually, with a pronounced seasonal pattern classified as flat year-round. The worst month is March at AQI 76 (Satisfactory) and the cleanest is July at AQI 34 (Good) — a 42-point swing between them. Severe days (AQI > 400) make up 0% of the record while Good-or-Satisfactory days account for 96.2%.
The four seasons
Indian meteorological seasons: Winter (Dec–Feb), Summer (Mar–May), Monsoon (Jun–Sep), Post-monsoon (Oct–Nov).
Winter
AQI 63Summer
AQI 64Monsoon
AQI 37Post-monsoon
AQI 42Climograph — 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 | — | — | — | 69 | 40 | 26 | 16 | 18 | 19 | 25 | 36 | 59 | 34 |
| 2023 | 87 | 92 | 73 | 66 | 47 | 50 | 53 | 58 | 61 | 57 | 56 | 52 | 62 |
| 2024 | 48 | 57 | 79 | 84 | 56 | 34 | 23 | 22 | 29 | 33 | 43 | 50 | 48 |
| Avg | 68 | 70 | 76 | 74 | 49 | 38 | 33 | 36 | 42 | 39 | 45 | 55 | — |
Winter in Gangtok
Winter (Dec–Jan–Feb) in Gangtok averages AQI 63 across 181 measured days — Satisfactory on the NAQI scale. 0% of those days fall in Very Poor or Severe; 90.1% are Good or Satisfactory. Year-on-year, winter improved by 30.5% in the most recent comparison. Winter in Gangtok is not the headline season, but shallow morning inversions can still produce short spikes. Gangtok'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 42 (Good), versus 40 (Good) for the rest of October. 17 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 36 (Good), compared with an annual mean of 50.
Summer
Summer (Mar–Apr–May) in Gangtok averages AQI 64 across 186 measured days — Satisfactory on the NAQI scale. 0% of those days fall in Very Poor or Severe; 93.5% are Good or Satisfactory. Year-on-year, summer worsened by 17.5% in the most recent comparison. Summer air in Gangtok 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. Gangtok's summer mean of 64 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 Gangtok averages AQI 37 across 271 measured days — Good on the NAQI scale. 0% of those days fall in Very Poor or Severe; 100% are Good or Satisfactory. Year-on-year, monsoon improved by 51.9% in the most recent comparison. The Jul 15 – Sep 15 core monsoon window averages AQI 36, a 28% improvement on the annual mean of 50. 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 Gangtok.
Post-monsoon
Post-monsoon (Oct–Nov) in Gangtok averages AQI 42 across 150 measured days — Good on the NAQI scale. 0% of those days fall in Very Poor or Severe; 100% are Good or Satisfactory. Year-on-year, post-monsoon improved by 35.1% in the most recent comparison. Post-monsoon in Gangtok 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 Gangtok is worsening overall — AQI moved from 34 in 2022 to 48 in 2024, a +41.2% change. No month shows a material worsening of 10% or more. No month shows a material improvement of 10% or more. Because Gangtok's seasonal shape is flat year-round, policy action that targets the March 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 48-45%
Jan in Gangtok averages AQI 48 (Good) in the most recent year, having moved from 87 in 2023. Direction: improving (-44.8%).
Feb2023–2024Latest AQI 57-38%
Feb in Gangtok averages AQI 57 (Satisfactory) in the most recent year, having moved from 92 in 2023. Direction: improving (-38.0%).
Mar2023–2024Latest AQI 79+8%
Mar in Gangtok averages AQI 79 (Satisfactory) in the most recent year, having moved from 73 in 2023. Direction: stable (+8.2%).
Apr2022–2024Latest AQI 84+22%
Apr in Gangtok averages AQI 84 (Satisfactory) in the most recent year, having moved from 69 in 2022. Direction: worsening (+21.7%).
May2022–2024Latest AQI 56+40%
May in Gangtok averages AQI 56 (Satisfactory) in the most recent year, having moved from 40 in 2022. Direction: worsening (+40.0%).
Jun2022–2024Latest AQI 34+31%
Jun in Gangtok averages AQI 34 (Good) in the most recent year, having moved from 26 in 2022. Direction: worsening (+30.8%).
Jul2022–2024Latest AQI 23+44%
Jul in Gangtok averages AQI 23 (Good) in the most recent year, having moved from 16 in 2022. Direction: worsening (+43.8%).
Aug2022–2024Latest AQI 22+22%
Aug in Gangtok averages AQI 22 (Good) in the most recent year, having moved from 18 in 2022. Direction: worsening (+22.2%).
Sep2022–2024Latest AQI 29+53%
Sep in Gangtok averages AQI 29 (Good) in the most recent year, having moved from 19 in 2022. Direction: worsening (+52.6%).
Oct2022–2024Latest AQI 33+32%
Oct in Gangtok averages AQI 33 (Good) in the most recent year, having moved from 25 in 2022. Direction: worsening (+32.0%).
Nov2022–2024Latest AQI 43+19%
Nov in Gangtok averages AQI 43 (Good) in the most recent year, having moved from 36 in 2022. Direction: worsening (+19.4%).
Dec2022–2024Latest AQI 50-15%
Dec in Gangtok averages AQI 50 (Good) in the most recent year, having moved from 59 in 2022. Direction: improving (-15.3%).
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 Gangtok.
Opposite seasonal profile
Cities whose seasonal signature least resembles Gangtok.
What to do with this information
If you are choosing when to visit Gangtok or plan outdoor events — marathons, weddings, school sports, outdoor festivals — the CPCB record says July 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 March in Gangtok 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 Gangtok?
March is the most polluted month in Gangtok on average, with a long-run AQI of 76 — firmly in the Satisfactory band. This is drawn from 1 CPCB monitoring stations across 3 years of daily readings. Through March, 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 Gangtok?
July is the cleanest month of the year in Gangtok, averaging AQI 34 in the Good band. The months immediately before and after also tend to sit well below the annual mean of 50, so a visit window centred on July 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 Gangtok's air spike in March?
Gangtok's profile is relatively flat year-round; the small March reflects modest swings in wind, rainfall and local emissions rather than a dramatic seasonal mechanism.
How bad is Diwali air quality in Gangtok?
Across the CPCB record, the week around Diwali in Gangtok averages AQI 42 — 1.05× the normal October baseline of AQI 40, a spike of 2 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 Gangtok's air?
Yes — meaningfully. Gangtok's core monsoon window (Jul 15 – Sep 15) averages AQI 36, a 28% improvement on the annual mean of 50. Rain removes airborne particulates by wet deposition, and the deeper monsoon boundary layer disperses what remains vertically. Across 271 measured monsoon days we see 100% in the Good-or-Satisfactory band.
Is Gangtok's worst season getting worse or better year-on-year?
Between 2022 and 2024, Gangtok's annual average AQI moved from 34 to 48 — a change of +41.2%. In the most recent year-on-year comparison, the winter season specifically improved by 30.5%. The long-run direction is worsening — rapid urbanisation and emissions growth appear to be outpacing efficiency gains.
Which months are safest to visit Gangtok?
July is the single best month at AQI 34. Based on the 12-month averages, the three cleanest months in Gangtok are July (AQI 34), August (AQI 36), June (AQI 38). 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 March, when the baseline jumps into Satisfactory territory.
How does Gangtok's seasonal pattern compare to other Indian cities?
Gangtok is classified as flat year-round. Based on a 12-month cosine-similarity index computed across all monitored Indian cities, the city whose seasonal signature most closely resembles Gangtok's is Ariyalur (Tamil Nadu), with its own worst month in March. 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 Gangtok too. The peer-city panel on this page lists the closest four additional matches.