London is about to get its first proper taste of autumn. After an October that has so far felt more like an extension of summer, the Met Office expects overnight temperatures to plunge into single digits across the capital, with the coldest spots dipping to just 6C in the early hours of Tuesday.
It will be quite the contrast with Monday’s daytime weather. Highs are expected to reach up to 23C in the warmest parts of the capital on Monday, slipping to around 21C on Tuesday — still pleasant enough in the afternoon sun. But once darkness falls, clear skies will let the day’s warmth escape rapidly, and the mercury will tumble.
By Tuesday morning, thermometers across Greater London are expected to show single figures, with 6C likely in the chilliest spots. For early risers and the morning commute, it will feel like a different season entirely — worth digging out a proper coat and allowing a few extra minutes to clear the car if you park on the street.
Why frost can form even above freezing
One quirk of nights like these is that frost can appear on grass, garden furniture and car windscreens even when the forecast air temperature stays a degree or two above zero. On clear, calm nights the ground cools faster than the air, so surfaces can drop below freezing while the official reading — taken a couple of metres above the ground — remains slightly milder.
Ground frost is far more common than air frost at this time of year, and that distinction matters for gardeners: tender plants can be damaged on a night when the headline temperature never technically reaches freezing.
Is a cold snap like this normal for October?
Completely. Single-digit nights are a normal feature of October in London, not a freak event. The Met Office’s long-term averages for Heathrow (1991–2020) show the average September minimum at 10.2C falling to just 7.3C in October — so the night ahead is right on schedule.
Heathrow averages around one air-frost night (about 1.1 days) each October, and ground frosts are more frequent still. Air frosts remain the exception rather than the rule this early in autumn, and none are expected in central London this week.
The drop will feel sharper because of what came before. September ranked among the warmest on record, with the capital reaching 28.1C at its peak, and only days ago London was basking in 21C autumn sunshine with barely a cloud in the sky. From sun cream to scarves in the space of a fortnight — that is autumn in London for you.
Rain returns on Wednesday
The chill will not hang around for long. Cloud and rain are expected to move in on Wednesday, pushing temperatures back towards the seasonal average and ending the run of crisp, clear nights. Looking further ahead, the Met Office outlook for 19 October to 2 November leans above average, suggesting autumn still has some milder spells up its sleeve.
What Met Office yellow warnings actually mean
No weather warnings are currently in force for this cold snap, but it is worth knowing how the Met Office system works for when they are. Warnings come in three colours. A yellow warning means “be aware”: the weather could disrupt daily life, travel plans may need adjusting, and forecasts should be checked for updates.
An amber warning steps things up to “be prepared”, with a greater likelihood of significant disruption, while a red warning — the rarest — means “take action” to protect yourself, as dangerous weather is expected. Warnings are issued when the Met Office believes impactful weather is likely, and they are updated as forecasts firm up. Before any journey in unsettled weather, it is always worth checking the latest Met Office warnings page.
Getting your home and garden ready for the cold snap
The first cold night of autumn is a useful nudge to get winter-ready. A few simple jobs now can save hassle later:
- Move tender potted plants under cover, or wrap pots in fleece — the first ground frost of the season is the one that catches most gardeners out.
- Lag any exposed outdoor taps and check pipe insulation, particularly in unheated outbuildings and lofts.
- Give the boiler a test run and bleed any cold spots out of radiators so the heating works efficiently when you need it.
- Dig out the draught excluders and check window seals — small gaps can make a surprising difference to heating bills.
- Keep an eye on older neighbours and relatives. Cold homes pose a genuine health risk, and a quick check-in costs nothing.
For now, make the most of Monday’s warmth — by Tuesday morning, London will feel unmistakably autumnal. And if you are heading out early, that coat you packed away in May is about to earn its keep.
