Pakistan -- home to more than 240 million people -- ranks among the countries most vulnerable to the effects of climate change, which scientists say is making extreme weather events more common and more severe.

The Pakistan Meteorological Department (PMD) says the farming heartland of eastern Punjab province saw 42 percent less rainfall than normal between the start of September and mid-January.

"The lack of rains has had a major financial impact on farmers, whether they have a big holding or a small one," Fruit and Vegetable Exporters Association Punjab chairman Malik Asghar told AFP.

"Potato is a staple in my area. The average is very low this year. Usually we could easily get 100 to 120 sacks per acre. This winter we have only gotten about 60 sacks per acre."

The agriculture sector contributes nearly a quarter of Pakistan's GDP and employs 37 percent of the national labour force, according to the UN's Food and Agriculture Organization.

But Asghar said many small farmers "were already giving up" and looking for employment elsewhere.

"This spell of dry weather will have a very adverse reaction on them," he said.

Sindh, Pakistan's most urbanised province located in the south, witnessed rainfall 52 percent below normal levels according to the PMD, while Balochistan in the west saw a 45 percent drop.

"Mild drought" prevailed in most of Punjab, all of Sindh and around half of Balochistan in January according to the PMD, which predicts rapidly onsetting "flash droughts" in the warmer months to come.

Wheat farmer Ishfaq Ahmad Jatt said his harvest in the Multan area of central Punjab has been "badly affected" by the dearth of rain.

"Even five years ago we used to get winter rains for a week at a time. They were light rains but they were enough for us," the 45-year-old said.

"If it doesn't rain soon, you can expect production to drop by as much as 50 percent."

Pakistan generally relies on water from the Indus river which bisects the country from north to south, where it empties into the Arabian Sea.

But analysts say a fast-growing population, climate change and poor resource management with an over-reliance on a single water source are all spurring scarcity.

The drought comes less than three years since record monsoon rains caused devastating floods that left nearly a thirds of the country under water -- including the major agricultural areas of Sindh and Punjab.

The country also suffers from choking smog in the winter season, caused by poor quality vehicle fuel and farmers burning off crop remnants, with cold weather trapping pollution close to the ground.

Rain typically offers temporary reprieve by dampening down airborne particles, but the dry weather has seen Punjab province blanketed by smog with hazardous health effects.