Observations refresh every thirty minutes. The verdict on each card is ours, not the operator’s, and it is conservative on purpose.
What flyable, marginal and grounded mean
Flyable. Visibility and wind are inside normal operating limits for the airstrip. Flights should run close to schedule.
Marginal. There is a window, but it may close. Expect holds, expect the later departures to be at risk, and do not build a same-day international connection behind a marginal morning.
Grounded. Conditions are outside visual flight limits. Nothing is going, and the honest advice is to plan for the day to be lost.
Why we publish a verdict rather than just numbers
A wind speed and a cloud percentage do not tell a trekker what they need to know. What they need to know is whether they are flying. We would rather take a position and be occasionally wrong in the conservative direction than present raw figures and let people talk themselves into optimism.
The limits of any weather page
This page reads a global forecast model. It does not see the cloud sitting in the Dudh Kosi gorge at seven in the morning, and it does not know that an aircraft is already holding at Phaplu waiting for it to lift. The pilot in command makes the dispatch decision using information no website has.
Use this page to plan. Use the dispatch desk to decide.
The pattern of a Himalayan flying day
Mornings are better than afternoons, almost without exception. Overnight cooling settles the air, and the first flights of the day go out into the calmest, clearest conditions available. As the sun works on the valley walls, convection builds, cloud forms over the ridges and wind accelerates through the valleys. By early afternoon the Khumbu is frequently unflyable even on a day that started perfectly.
This is why every scheduled departure we publish is a morning one, and why the single afternoon slot on the Kathmandu to Lukla route is the first thing we cancel.