A Met Office outlook pointing to heatwave conditions in London in September 2026 has been doing the rounds, and it is a timely reminder that the UK's shoulder season no longer guarantees mild, drizzly days. The source coverage, from London-focused outlet Secret London, flags an extended spell of unseasonably warm weather hitting the capital just as most visitors expect to pack jumpers.

September has quietly become one of London's best months in recent years. School holidays are over, the big summer crowds thin out, and hotel rates often dip from their August peaks. The catch, when a heatwave rolls in, is that the city is not built for it. Many older hotels, pubs and Tube carriages lack air conditioning, and deep Tube lines can feel like ovens during a hot commute. Parks and riverside spots, on the other hand, come alive — Regents Park, Hampstead Heath's bathing ponds and the South Bank all shine in warm evening light that stretches well past 7pm in early September.

If you are planning a city break around this period, build your days like a local does in a hot spell. Do indoor heavy-hitters — the British Museum, the National Gallery, Borough Market under cover — during the midday peak, and save walks, park picnics and rooftop bars for mornings and early evenings. Book accommodation with air conditioning or at least a fan if you can; it is not a given at the mid-range level. And keep a light rain layer handy anyway, because British forecasts at range can shift quickly, and what starts as a heatwave can end in a thundery downpour.

For travellers, the takeaway is simple: September is a great time to be in London, arguably better than July or August once you factor in prices and queue times. Just do not assume autumn means cool weather. Check the Met Office forecast in the week before you fly, pack breathable layers and sunscreen alongside the waterproof, and book any afternoon-time-out attractions in advance so you are not standing in a long outdoor queue at 2pm.

Worth noting: this story is based on early forecast coverage, and long-range UK weather outlooks are notoriously changeable. Treat the heatwave call as a trend to watch rather than a guarantee — but either way, a late-summer-warm London trip has a lot going for it, from open-air cinema and theatre seasons to riverside festivals running into autumn.