Pakistan lies in a temperate zone and its climate is as varied as the country’s topography—generally dry and hot near the coast and along the lowland plains of the Indus River, and becoming progressively cooler in the northern uplands and Himalayas. Four seasons are recognized: 1) a cool, dry winter from December to February; 2) a hot, dry spring from March through May; 3) the summer rainy season, also known as the southwest monsoon period, occurring from June to September; and 4) the retreating monsoons from October to November. A majority of the country receives very little rainfall, with the exception of the Northern regions, where monsoons can bring upwards of 200 mm a month from July to September. Inter-annual rainfall varies significantly, often leading to successive patterns of floods and drought. El Niño is a significant influence on climate variability in Pakistan, with anomalies in both temperature and flood frequency and impact correlated with the El Niño cycle.
- Warming in Pakistan was estimated at 0.57°C over the 20th century, but has accelerated more recently, with 0.47°C of warming measured between 1961–2007.
- Increases in temperature is strongly biased towards the winter and post-monsoon months (November–February). On a sub-national level, warming is also strongly biased towards the more southerly regions, with Punjab, Sind, and Baluchistan all experiencing winter warming in the region of 0.91°C–1.12°C between 1961–2007, and Khyber Pakhtunkhwa in the north experiencing only 0.52°C.
- The rise in average daily maximum temperatures (0.87°C between 1961–2007) has been slightly stronger than the rise in average temperatures. A concurrent increase in the frequency of heat wave days has been documented, particularly in Sindh Province.
- Mean rainfall in the arid plains of Pakistan and the coastal belt has decreased by 10-15% since 1960. Most other regions have experienced a slight increase, seen both in the monsoon and dry seasons.
- The number of heavy rainfall events has increased since 1960, and the nine heaviest rains recorded in 24 hours were recorded in 2010.
- Recent evidence suggests that glaciers in the headwaters of the Indus Basin may be expanding due to increased winter precipitation over the Himalayan region in the last 40 years.