Heathrow weather: what to expect, and when it affects your flight

For today and the next few days, use the Met Office forecast for Heathrow, linked in the panel beside this page. There is a deliberate reason this page does not print a temperature: these pages are static, rebuilt when the facts change rather than every hour, and a number baked into the HTML would be wrong more often than it was right. The same rule applies to the live security queue and to today's delays.

The Met Office is the right source rather than a default one. It operates the climate station at Heathrow itself, so the airport forecast is not interpolated from somewhere else, and it is the service UK airlines and air traffic control work from. If a named storm or a weather warning is running, the Met Office warnings page for the area is the thing to read, because a yellow or amber wind warning is the earliest reliable signal that a flying day is going to be untidy.

What the forecast will not tell you is whether your particular flight is affected. That only shows on the boards. Check Heathrow departures or Heathrow arrivals on the day, and check your airline's app as well, because airlines usually cancel and re-book before the airport board catches up.

If you have noticed that Heathrow comes up whenever the weather makes the news, that is not a coincidence about aviation. Heathrow is one of the UK's long-running reference climate stations, recording continuously since 1948, and it sits on the airfield rather than in a nearby village. When a bulletin reports a national temperature record, there is a fair chance the figure was measured here.

That has a practical consequence for anyone reading this page. The numbers below are measurements taken at the airport, not an estimate for the general area. Of the four big airports, Heathrow is the only one whose published climate averages come from a station on the airport itself: Gatwick's nearest station is at Charlwood, Stansted's is at Andrewsfield, and Birmingham's is at Coleshill. Heathrow's figures are the airport's own.

These are the Met Office 1991 to 2020 averages for the Heathrow station: the standard 30-year reference period. Treat them as what a normal year looks like, not a forecast for yours.

Three things in that table are worth pulling out. The year totals about 615mm of rain, which is drier than most people assume: the Charlwood station next to Gatwick, 25 miles south, records 834mm, so Heathrow gets roughly a quarter less rain than the other big London airport. Rainfall is also flatter across the year than the British reputation suggests, sitting between 39mm and 67mm every single month, so there is no dry season to aim for and no monsoon to avoid.

Frost is where Heathrow really separates from its neighbours. It averages 27 days of air frost a year, against 53 at Charlwood by Gatwick and 42 at Coleshill by Birmingham Airport. West London sits inside the urban heat island, and the airport's own concrete and traffic add to it, so overnight temperatures hold up and hard frosts are less common. For a traveller that mostly matters in one way: de-icing delays on winter mornings are less frequent here than at the airports outside the city.

If you want this in packing terms rather than numbers, the seasonal guidance for visitors is on first time in the UK, which covers what a British trip actually calls for. This page stays on the airport and the flying.

Most weather does not delay flights. Rain does not, and neither does ordinary cold, ordinary heat or ordinary cloud. Modern aircraft take off in conditions that look dramatic from the terminal window. Three things genuinely disrupt Heathrow, and only one of them is common.

Fog is the big one. It rarely closes the airport, because the runways carry an instrument landing system good enough to land in very low visibility and most long-haul aircraft and crews are certified for it. What fog does is force air traffic control to put bigger gaps between arriving aircraft, which cuts the number of landings possible each hour. Heathrow is the airport where that hurts most, because it runs at close to full capacity on two runways with almost no spare slots to absorb a reduced arrival rate. A foggy autumn morning at Heathrow reliably produces delays and a batch of short-haul cancellations, and the knock-on runs through the day as aircraft and crews end up out of position.

Strong wind is the second. Heathrow's two runways both run roughly east to west, which suits the prevailing westerly. A strong wind blowing across that line is the awkward one, and named storms are the usual cause. Crosswind limits vary by aircraft type, so in a storm you often see smaller regional aircraft cancelled while larger ones keep operating. Winter storms are also the case where airlines pre-emptively thin the schedule a day ahead, so check your flight the evening before rather than on the morning.

Snow is the rare one. With 27 frost days a year, settling snow is an occasional event rather than an annual one. When it comes, the limit is not whether aircraft can fly but how fast the airport can de-ice them and keep the runways clear, both of which take time per aircraft. The pattern is a thinned schedule for a day or two rather than a closure.

In all three cases the honest advice is the same. The forecast tells you whether disruption is plausible; only the live boards and your airline tell you whether it is happening to you.

This is where weather delays differ from other delays, and it catches people out. Weather severe enough to make flying unsafe counts as an extraordinary circumstance under the UK261 rules, and an extraordinary circumstance releases the airline from paying compensation. So the fixed cash payouts you may have read about, the ones that run into the hundreds of pounds, do not apply to a fog morning or a storm.

What does still apply is the duty of care, and it applies no matter what caused the delay. Once you pass two hours late on a short-haul flight, three hours on medium-haul or four hours on long-haul, the airline has to provide meals and refreshments appropriate to the wait, plus two phone calls or emails. If the delay pushes you into the next day, it has to provide a hotel and the transport to it. If your flight is cancelled outright, you keep the right to choose between a full refund and re-routing to your destination, again regardless of the weather.

Two practical notes. Airlines do not always volunteer the duty of care during weather disruption, when the desks are busiest, so ask. And if you end up paying for a meal or a room yourself because nobody was available to arrange it, keep every receipt and claim afterwards: reasonable costs are recoverable even when compensation is not. The full detail, including how to escalate to the Civil Aviation Authority, is on Heathrow passenger rights.