ISLAMABAD: A spell of heavy rain accompanied by intense hail struck parts of Islamabad on Thursday, September 24, with residents reporting unusually large hailstones.

Images from the capital showed sizeable chunks of ice collected after the storm, raising questions about what produces such large hail and whether climate change is increasing the risk of severe weather events of this kind.

While a single hailstorm cannot scientifically be attributed to climate change without a dedicated attribution study, researchers say global warming is changing several atmospheric conditions that influence thunderstorms, heavy rainfall and hail.

How do such large hailstones form?

Hail develops inside powerful thunderstorm clouds rather than simply forming because the air near the ground is cold.

According to the US National Severe Storms Laboratory, strong upward-moving currents of air, known as updrafts, carry water droplets high into a thunderstorm where temperatures are well below freezing. The droplets freeze and then grow as additional supercooled water freezes onto them.

The stronger the updraft, the longer a hailstone can remain suspended inside the cloud and the larger it can become. Eventually, when the ice becomes too heavy for the rising air to support, it falls to the ground.

Very large hail is therefore generally associated with thunderstorms containing particularly strong and sustained updrafts.

Several ingredients can contribute to a severe hailstorm, including abundant atmospheric moisture, strong instability, freezing temperatures high inside the cloud, supercooled liquid water and powerful vertical air currents.

Where does climate change come in?

The connection between climate change and hail is more complicated than the relationship between global warming and heatwaves.

A warmer atmosphere can contain more water vapour, roughly 7% more moisture for every 1°C of warming under ideal conditions. Greater atmospheric moisture can provide additional fuel for intense rainfall and powerful convective thunderstorms when other weather conditions are favourable.

Those stronger convective environments can, in some situations, generate more vigorous updrafts capable of supporting larger hailstones.

A major scientific review published in Nature Reviews Earth & Environment found that human-caused warming is expected to increase low-level atmospheric moisture and convective instability, conditions that can favour hail formation and potentially larger hailstones. However, researchers stressed that the response varies considerably between regions.

There is also an important counter-effect. As the climate warms, the altitude at which temperatures fall below freezing generally rises.

Hailstones therefore have to travel through a deeper layer of warm air before reaching the ground, causing smaller pieces of hail to melt. Consequently, climate change does not necessarily mean more hailstorms everywhere.

In some places, smaller hail may become less common while the most severe hail events become more damaging.

New research points to growing large-hail risk

Research published in Nature in May 2026 projected an increase in global hail-related damage potential later this century under continued warming.

The modelling suggested a shift toward larger hailstones globally, although changes differ sharply by region and some tropical and monsoonal areas may experience different trends.

Another 2026 study in Nature Climate Change similarly found that future hail risk is geographically complex, with hail-prone conditions potentially shifting as the planet warms.

Researchers cautioned that uncertainty remains particularly high in tropical and monsoon-influenced regions.

That qualification is particularly important for Pakistan.

Pakistan already faces a changing climate

Pakistan has experienced a clear warming trend, while changes in rainfall are more complicated and vary considerably by location and season, according to the World Bank's Climate Change Knowledge Portal.

There is stronger evidence connecting climate change with some of Pakistan's extreme rainfall events.

Following the catastrophic 2022 floods, a World Weather Attribution analysis reported by the World Meteorological Organization concluded that human-caused climate change had likely increased the intensity of extreme rainfall in Pakistan, although substantial uncertainty remained over the precise magnitude of the effect.

That finding does not prove that Islamabad's latest hailstorm was caused by climate change, but it illustrates how a warming climate can alter the background conditions in which extreme weather develops.

Can Islamabad's hailstorm be directly attributed to climate change?

Scientists would need detailed information including local temperature and humidity profiles, radar observations, atmospheric instability, wind shear, freezing-level height and long-term records of hail frequency and size in the Islamabad-Rawalpindi region.

Climate models would then need to compare the likelihood of such an event in today's warmer climate with a hypothetical climate without human-caused warming.

Without such an analysis, the scientifically accurate conclusion is that climate change may be influencing some of the atmospheric ingredients capable of producing severe hail, but it cannot be identified as the sole cause of this particular Islamabad storm.

What the latest research does indicate is that global warming is reshaping severe thunderstorms in complicated ways.

In some areas, the result may not necessarily be more hail days, but when conditions are right, the atmosphere may increasingly be capable of producing larger and potentially more damaging hailstones.