Punjab province's education minister Rana Sikander Hayat said summer vacations will now start from May 28 instead of June 1.

Class times have also been changed, with all educational institutes instructed to close two hours early at 11:30 am "due to a constant heatwave", a notification issued by the education department said.

Pakistan, one of the countries most vulnerable to the effects of global warming, has been experiencing unusually high temperatures after a particularly dry winter.

Temperatures soared to near-record highs for the month of April, reaching as high as 46.5 degrees Celsius (115.7 degrees Fahrenheit) in parts of Punjab.

An alert issued on Monday by the national meteorological agency forecast that northern parts of the province, currently in the grip of a heatwave, will see daytime temperatures rise "5 to 7C above normal".

An Education Department representative told AFP the early closures were announced because of the weather.

"We had to move up the summer vacation schedule because of these heatwaves," the representative said.

Schools in the province that serve tens of millions of children also closed for a week in May last year because of excessive heat, and for several weeks in November because of high levels of toxic smog that blanketed several cities.