A "severe heatwave" that was prevailing over central and upper Sindh is forecast to grip the entire province — including Karachi — for nearly a week from May 11 with the maximum temperature projected to exceed 40 degrees Celsius in the provincial capital, the Pakistan Meteorological Department (PMD) said on Sunday.

In its heatwave advisory, the Met department said the weather in the metropolis would remain hot next week, predicting the heatwave spell could last till May 16.

"The maximum temperature in Karachi may rise to 40°C and more during May 12 and 14."

It predicted that the temperature in the city would likely be in the range between 35°C and 38°C from May 9 to 10 before intensifying by May 11 to 12.

The PMD also predicted "extreme heatwave" in other parts of the province, saying the daytime maximum temperatures in Dadu, Sukkur, Larkana, Jacobabad, Shaheed Benazirabad (Nawabshah), Naushero Feroz, Khairpur, Shikarpur and Ghotki districts would rise to 46 to 48 °C.

While in Jamshoro, Hyderabad, Badin, Thatta, Mirpurkhas and Umerkot districts, the temperatures could peak at 45 °C during the period.

The department warned that hot and dry conditions could cause stress on crops, vegetables and orchards, and increase energy demands.

It also advised the public to avoid open sun exposure as much as possible, especially during peak hours (11am to 4pm).

A day ago, top climate scientists said the devastating heatwave that gripped Pakistan and India over the last two months was unprecedented, but worse — perhaps far worse — was on the horizon as climate change continues apace.

“This heatwave is likely to kill thousands,” said Robert Rohde, lead scientist at Berkeley Earth, a climate science research non-profit.