Kollam — Seasonal Pollution Patterns

January is the most polluted month in Kollam on average, with a long-run AQI of 104 — firmly in the Moderate band. This is drawn from 1 CPCB monitoring stations across 5 years of daily readings. Through January, 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.

July is the cleanest month of the year in Kollam, averaging AQI 66 in the Satisfactory band. The months immediately before and after also tend to sit well below the annual mean of 84, 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.

Kollam's profile is relatively flat year-round; the small January reflects modest swings in wind, rainfall and local emissions rather than a dramatic seasonal mechanism.

Across the CPCB record, the week around Diwali in Kollam averages AQI 103 — 1.35× the normal October baseline of AQI 76, a spike of 27 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.

Only partially. Kollam's monsoon window averages AQI 74, which is a 11.9% change from the annual mean of 84. Rain does scrub particulates, but the improvement here is modest — pointing to persistent local sources (industry, traffic, dust) that rain cannot fully wash away.

Between 2020 and 2024, Kollam's annual average AQI moved from 86 to 84 — a change of -2.3%. In the most recent year-on-year comparison, the winter season specifically worsened by 21.1%. The long-run direction is roughly stable — underlying growth in emissions is being offset by cleaner technology or weather variability.

July is the single best month at AQI 66. Based on the 12-month averages, the three cleanest months in Kollam are July (AQI 66), June (AQI 68), May (AQI 70). 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 January, when the baseline jumps into Moderate territory.

Kollam 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 Kollam's is Kozhikode (Kerala), with its own worst month in January. 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 Kollam too. The peer-city panel on this page lists the closest four additional matches.