A glacial lake outburst flood, or GLOF, is a sudden flood when a lake held back by ice or loose glacial debris breaks through. In northern Pakistan the risk is highest in the warm months, roughly May to September, when melt raises lake levels, and it is highest in the side valleys of Hunza, Nagar, Ghizer and Chitral. For a traveller the realistic danger is not being caught by a flood in a town, but a blocked road, a washed-out bridge or a camp pitched beside a stream.
This guide explains what the risk is, where recent events have happened, and how to plan for it. It is a practical note, not a reason to cancel: most trips to the north pass without incident. For the wider seasonal picture, see our when to go guide.
| At a glance | |
|---|---|
| Main risk period | Roughly May to September, with melt at its highest in summer |
| Places most affected | Side valleys of Hunza, Nagar, Ghizer (Gupis, Ishkoman), Chitral and Swat |
| Recent events | Shishper (Hunza) May 2022; Gupis, Ghizer 22 August 2025; Ishkoman, Ghizer 8 July 2026 |
| Typical impact on visitors | Road and bridge closures, delays, damage to riverside camps and guesthouses |
| Where to check | PMD and NDMA alerts, hotel owners, local police and the NHA on road status |
What is a GLOF?
Warming temperatures create new glacial lakes or enlarge old ones, often dammed by loose rock and ice. If the dam fails, or the lake overflows, the water and debris surge down the valley within minutes to hours.
Pakistan has a very large number of glaciers: more than 13,000 according to its 2024 inventory, as reported by Dawn. The country's space agency SUPARCO monitors the glacial lakes by satellite. Its assessment as of 5 August 2026 counted 105 unfrozen lakes, up from 40 a month earlier, and identified 131 potentially dangerous glacial lakes. Earlier estimates from organisations working on GLOF risk reduction put the number of hazardous lakes across Gilgit-Baltistan and Khyber Pakhtunkhwa at about 33 out of more than 3,000.
Figures differ depending on the year and the method used, so treat them as an indication that the risk is real and monitored, not as an exact count.
Recent events travellers should know about
- Shishper glacier, Hassanabad, Hunza (7 May 2022). An ice-dammed lake formed behind the surging Shishper glacier drained suddenly and swept away the Hassanabad bridge on the Karakoram Highway, damaging houses, farmland and two small hydropower plants. Timely warnings meant no lives were lost, according to reports. It cut the highway, which matters for anyone travelling between Hunza and the rest of the country.
- Gupis Valley, Ghizer (22 August 2025). A flood destroyed or severely damaged more than 330 homes, formed a lake about 7 km long behind a debris dam and damaged roads and bridges. Army teams evacuated more than 200 people. A shepherd who spotted the signs and phoned the village is credited with the early warning.
- Ishkoman Valley, Ghizer (8 July 2026). A GLOF caused flash flooding, debris flows and riverbank erosion, according to Community World Service.
- PMD alert, 10 to 11 May 2026. The Pakistan Meteorological Department issued a GLOF alert covering Hunza, Nagar, Ghizer, Ghanche, Shigar, Astore, lower Chitral, Swat, Dir and Kohistan during a westerly weather system, and told tourists to avoid unnecessary movement near streams and rivers.
What it means for a trip
The roads
The commonest effect is a blocked or damaged road. The Karakoram Highway through Hunza, the Gilgit to Ghizer road towards Gupis and Shandur, and the side valleys leading to villages are all exposed. Closures can last hours or weeks. Build in at least one spare day around any long transfer in summer, and do not book a same-day flight home from Islamabad after a mountain leg.
Camping and accommodation
The greatest danger for visitors is near water. Do not camp on riverbanks, in dry stream beds or on alluvial fans at the mouth of a side valley. Choose hotels and campsites on higher, established ground and ask the owner about past flooding.
Trekking
Treks through glacier-fed valleys cross streams that rise quickly on hot afternoons and after rain. Cross early in the day, and talk to guides about the route. Our trekking season guide for Gilgit-Baltistan covers timing.
Warning signs and what to do
Warning signs are often local and simple. A stream that suddenly drops or turns muddy, a rumbling or crashing sound upstream, or a sudden change in water colour can all mean a blockage or a release.
- Move to high ground immediately, away from the river, not along the valley floor.
- Do not cross or wait to watch. Debris and boulders travel with the water.
- Tell people nearby and phone the hotel or police.
- Check official alerts each morning in summer: PMD and NDMA warnings, and local road updates.
- Follow local instructions. Villages near dangerous lakes often have their own warning arrangements.
Is it safe to travel in the north in summer?
For most visitors, yes, with sensible planning. Pakistani families and overseas travellers continue to visit Hunza and Gilgit-Baltistan in summer, and the risk to any one traveller is small. Gilgit-Baltistan itself is not on the UK government's list of areas advised against, but the Karakoram Highway between Mansehra and Chilas is (all travel, updated 22 September 2026), the Babusar route avoids it in summer, and the UK also advises against travel to Swat, Dir and the Kalash valleys. Foreign-passport holders should check their own advice, since it can void travel insurance, and everyone should check local news and police advice before setting out.
Who should worry, and who should not
If you are travelling on main paved roads, staying in established hotels and building in spare days, the GLOF risk is one to be aware of rather than to fear. If your plan is a remote trek, a riverside camp or a tight schedule, it deserves more attention, and it may be better to travel in June or September rather than July and August.
If you want a trip planned around weather and road closures, our Gilgit, Hunza and Khunjerab tour runs on the main Karakoram Highway corridor, and you can compare routes on our tours page.
Frequently asked questions
What is a GLOF?
A glacial lake outburst flood: a sudden release of water from a lake held back by ice or glacial debris.
When is the GLOF risk highest in Pakistan?
Roughly May to September, when heat melts snow and ice and raises lake levels. PMD has issued alerts as early as May.
Which areas have GLOF risk?
Hunza, Nagar, Ghizer, Ghanche, Shigar, Astore, Chitral and other glaciated valleys. Recent events include Hunza in 2022 and Ghizer in 2025 and 2026.
Is Hunza safe from GLOFs?
Most of it is not directly at risk, but side valleys such as Shishper have flooded and cut the Karakoram Highway. Check road status before travelling.
How do I check current GLOF warnings?
Look at PMD and NDMA alerts, ask your hotel and local police, and check road updates before leaving each morning.
