In the Punjab province of Pakistan, the monsoon rain can be divided into three distinct regions according to the amount of rainfall and its reliability.
The Heavy rainfall High Reliability Region
This comprises the North and Northeastern divisions of Punjab, namely the Rawalpindi and Gujranwala Divisions. Typical representative stations are the Hill station of Murree and the Plateau of Rawalpindi in the Rawalpindi division and the piedmont plains around Sialkot in the Gujranwala division,
Murree gets the most rain; as much as 35 inches in the three months of June, July and August with a frequency of one heavy downpour every other day, followed by Rawalpindi receiving not less than 28 inches in the aforesaid months. The No. of rain days are 10-12 in the monsoon months.
Sialkot, in the Gujranwala division, stands third both in the amount as well as frequency of the rainfall. Here the rainfall in the monsoon months is about 25 inches with 8-9 rain days in each of the monsoon months.
The common feature of all of the above mentioned three stations is not the amount but most prominently the reliability of rainfall. This is quite extraordinary at these locations. The rainfall amount varies only +/- 10 percent of the average in the normal years and even in the worst years it does not vary much beyond 15 percent.
The Moderate Rainfall and Low Reliability Region
This comprises of the East Central Punjab; Lahore is the chief representative of this region. Here rainfall amounts of the three months of July, August and September falls to about 17 inches and number of rain days fall to about 5-6 in the monsoon months. The amount of rainfall is not as important at Lahore as the low reliability or high variability of the monsoon rainfall. Every 3-4 years or so the rain can vary as much as 25 percent from the long term average. Some years are extraordinary. In August 1996 as much as 18 inches fell in three days in August whereas the total annual rainfall of Lahore is only 28 inches!
The Low Rainfall and Very Low Reliability Region
This covers a huge area. Actually it comprises of all district of Punjab other than the Northern, Northeastern and east Central Districts. The typical Station is the south western town of Multan. In Multan, only about 5-6 inches of rainfall is recorded in the three monsoon months, the no. of rain days are about 2-3 in each month. Moreover the rainfall amount is highly unreliable and extremely variable; sometimes as much as 10 inches can fall in 24 hours during a tremendously strong wet spell. This is more than total annual rainfall of Multan.
In short, less than one-third of the Province of Punjab in Pakistan gets reliable and heavy rainfall from the monsoons. The rest two-thirds of the province is not only deficient in rainfall but also gets highly variable precipitation from year to year during the monsoons.