Lahore Weather Today: Rain Window Opens, AQI Falls to 86

LAHORE: The Pakistan Meteorological Department’s rain window for Lahore opens on Monday evening, a day and a half after rain actually arrived, and the city’s air is the cleanest it has been this month — 86 on the live global board, down from 107 at the same reading on Sunday.

Both facts follow from the same weather. Sunday’s rain, which reached parts of the city at around 11am and was heaviest around the airport, ended a seven-day dry run and washed a large quantity of particulate out of the air. The system that produced it is the one the Met Office expects to strengthen from Monday.

In an advisory issued at 3:55pm on 11 September, the department said monsoon currents were penetrating upper parts of the country and that a westerly wave was likely to enter upper parts during the weekend and to strengthen on Monday, 14 September.

Rain-wind and thundershower activity, with isolated heavyfall and hailstorm, was expected in Lahore, Sialkot, Sheikhupura, Narowal, Mandi Bahauddin, Gujrat, Gujranwala, Wazirabad, Hafizabad, Kasur, Okara, Nankana Sahib, Sargodha, Khushab, Mianwali, Noorpur Thal, Faisalabad, Jhang, Toba Tek Singh, Layyah, Bhakkar, Sahiwal, Dera Ghazi Khan, Multan and surrounding areas from the evening and night of 14 September to 17 September, with occasional gaps.

On impacts, the department warned that heavy rains may cause urban flooding in low-lying areas of Islamabad and Rawalpindi, Peshawar, Mardan, Swabi, Gujranwala, Gujrat, Sialkot, Faisalabad and Lahore from 14 to 17 September. It also warned of flash flooding in local streams and nullahs across the northern districts, landslides in hilly areas of Khyber Pakhtunkhwa, Gilgit-Baltistan, Murree, Galliyat and Kashmir, and said temperatures were likely to drop during the forecast period.

Tourists and travellers were advised to remain cautious, farmers to manage crop activities in view of the conditions, and all concerned authorities to remain on alert. Daily updates are published at weather.gov.pk.

This is the ninth and probably final monsoon spell of the season. The Met Office has said the city’s weather is likely to improve after the rain.

Rescue 1122 can be reached on 1122, the PDMA helpline on 1129 and WASA’s complaint line on 1334.

Lahore seven-day weather forecast

Conditions were clear and 31°C at the time of writing on Monday morning.

The most useful thing in this table is the number that changed. Sunday’s update carried Monday at 5 per cent — the lowest figure in the week, on the day the Met Office expected the westerly wave to strengthen — and flagged the contradiction. Monday now carries 25 per cent, a fivefold revision in twenty-four hours, and Thursday has moved from 25 to 30 per cent.

That is the model converging on the advisory rather than the advisory being revised. Every day of the PMD’s stated window now carries a meaningful rain figure, and the two highest numbers in the table, Monday and Thursday, sit at the two ends of it. The temperature line has not changed materially: the week still ends cooler than it began, with the overnight minimum reaching 23 by Wednesday, four degrees below the 27 that held through the first half of September.

The table should still be read against the advisory rather than in place of it. Sunday was carried at 15 per cent and it rained.

Air quality: 86 and falling

Lahore was 19th of 125 cities on IQAir’s live global major-city board on Monday, at 86 — inside the Moderate band, and the first time this month the city has been out of the orange.

Three things are worth saying about that table.

The first is that 86 is a 21-point improvement on the same board in twenty-four hours, and a six-place fall down the global ranking. Baghdad led the board at 184, ahead of Jakarta at 168 and Kampala at 166. Lahore sat just below Kuwait City at 94 and just above Dubai at 86 and Delhi at 85 — a sentence this column does not often get to write in September.

The second is that IQAir’s own daily forecast, issued on Sunday, put Monday at 110. The live reading came in 24 points below the forecast. Post-rain air routinely undershoots models, because the models are estimating dispersion and the rain is doing removal, and removal is much faster.

The third is the caveat this column attached to exactly this figure on Sunday, and it has not changed. The global major-city board aggregates differently from IQAir’s Lahore city page, and on Sunday morning the two differed by 42 points at the same moment. A headline AQI figure is only as meaningful as the board it came from, and 86 is a global-board number. The city page had not published a refreshed Monday reading at the time of filing; its last full set, taken at 10:00 on Sunday, stood at 147 with PM2.5 at 54 micrograms per cubic metre and PM10 at 129.4.

Live readings are published by IQAir and by the Punjab Environmental Protection Agency at aqi.punjab.gov.pk.

The practical advice is simple and short-dated. Monday is a good morning to open windows, walk, and let children play outside. Sensitive groups — children, older residents, pregnant women and anyone with asthma, COPD or a heart condition — have a window of relief that will last as long as the weather does, and no longer.

Standing water and dengue

The health risk this week is not in the air. It is on the ground.

The district administration has already been ordered to accelerate drainage and eliminate stagnant water pools to stop dengue larvae breeding, and the province has ordered dengue surveys inside government offices alongside a third-party audit of the Lahore campaign.

With four consecutive days of rain now forecast, rooftop tanks, tyres, plant pots, discarded containers and construction hollows should be emptied as they fill, not once at the end of the week. Aedes larvae need roughly seven days of standing water to reach adulthood; a spell running from Monday evening to Thursday sets that clock going on Monday.

With the PMD warning of urban flooding in Lahore from Monday to Thursday, motorists should allow extra time on underpasses and low-lying stretches and avoid driving through standing water of unknown depth.

Analysis

Three numbers, four days, one city: 82 on Saturday afternoon, 147 on Sunday morning, 86 on Monday. Lahore’s emissions did not change across any of those readings.

Saturday was clean because there was wind. Sunday was dirty because the wind dropped to 3 kilometres an hour overnight and coarse particulate — road dust, construction dust, material lifted from unpaved surfaces — stopped being dispersed and nearly doubled, from 73 to 129.4 micrograms per cubic metre. Monday is clean because it rained on Sunday and the same particulate was washed out of the column altogether.

This is the argument this column made on Saturday and again on Sunday, and Monday is the third consecutive day it has held. It cuts both ways, deliberately. A low reading is not evidence that enforcement is working, any more than Sunday’s 147 was evidence that it had failed. The thermal drones now deployed across Punjab to track smog sources may well prove effective, and the dry-sweeping ban may well be removing real tonnage from the city’s air. Neither claim can be tested against a week in which the weather moved the number by 65 points. Only a seasonal average, compared year on year, can separate policy from weather, and this column will say so in November with the same emphasis it says so today.

What matters more than Monday’s figure is what Monday is. This is the last monsoon spell of the season. What follows it is the period in which Lahore’s air normally begins its decline: falling temperatures — which the PMD has now forecast explicitly, and which the table above already shows — lighter winds, a shallower mixing layer, and eventually stubble smoke drifting in from the wider Punjab.

Eighty-six is worth enjoying. It is not worth reading as a trend. The rain that produced it stops on Thursday, and the fortnight that follows the final monsoon spell is both the start of Lahore’s smog season and the most dangerous window of the year for dengue.