Karachi hits 41 degrees, its hottest September day in 10 years

Karachi reached 41 degrees Celsius on Monday, the city's highest September temperature in ten years. The Pakistan Meteorological Department puts the all-time September record at 43 degrees, set in 1951, with 42.7 degrees recorded on 20 September 2015.

It was not just Karachi. Nine cities across Sindh touched 40 degrees or above. Shaheed Benazirabad, Hyderabad and Khairpur were the hottest at 42 degrees.

Why the city cooked

Chief Meteorologist Ameer Hyder Laghari said a persistent low-pressure area sat over the region and blocked the sea breeze. Karachi's heat is almost always a sea breeze story: when the breeze comes in off the Arabian Sea the city is liveable in September, and when a pressure system parks itself and shuts the breeze off, the temperature climbs and the humidity stays.

Laghari also pointed to El Nino, the pattern of warmer surface water in the tropical Pacific, as a contributor to regional warming this season.

What Tuesday looks like

The low-pressure area has nearly dissipated, so PMD expects temperatures to fall from Tuesday. Karachi is forecast between 36 and 38 degrees. Relative humidity should run 70 to 80 per cent in the morning and drop to 45 to 55 per cent by evening.

That morning humidity is the part that matters for how it actually feels. Thirty-eight degrees at 75 per cent humidity is harder on the body than 41 degrees in dry air, which is why a lower forecast number this week will not feel like much of a break before noon.

The bill that follows

The system brought rain to some eastern parts of Sindh, but most of the province including Karachi got nothing, and PMD has already forecast a largely dry monsoon.

A dry, hot September means air conditioners running through the month on a bill cycle most households budget for as a shoulder month. A 1.5 ton inverter AC run eight hours a night is a serious line item at current slabs. Work out what your own unit adds with the AC running cost calculator, then check what those extra units do to your slab in the electricity bill calculator, which covers LESCO, IESCO, MEPCO and K-Electric.

The timing is poor: the DISCOs have asked NEPRA for Rs 1.73 a unit more from October, with a hearing on 29 September.

Staying safe in it

The standard advice holds and is worth repeating in a week like this. Drink water before you are thirsty, keep outdoor work off the 11am to 4pm window where you can, and watch for the warning signs of heat exhaustion: heavy sweating, dizziness, nausea, a headache that will not shift. Older people, small children and anyone working outside are at the highest risk.