CITY CLIMATE INSIGHTS
21 June 2026 - LocalRisk
Tropical nights are rare across most of the UK today, but Met Office UKCP18 projections show London, the South East and the warm southern coast pulling away as the climate warms - from about one a year now towards roughly fifteen in the capital at 4°C of warming.
How many tropical nights (overnight lows at or above 20°C) does your part of the UK get? Met Office UKCP18 projections by city and council - rare today, ri
A tropical night is a night when the air temperature never falls below 20°C. The Met Office uses it to mark overnight heat, and through the hot spells of recent summers it has crossed from forecasting jargon into the front pages. Health explains the attention. When the temperature holds above 20°C after dark, the body cannot shed the day's heat, sleep breaks up, and across a run of nights the strain on older people and anyone with a heart or lung condition builds. Night-time heat does more harm in a heatwave than the afternoon peak.
To most people in Britain a night that never drops below 20°C still sounds like somewhere else. The data agrees. The picture is moving, though, and it moves fastest where you would guess.
Tropical nights barely register across most of the UK. Recent observed data (ERA5 reanalysis via Open-Meteo, 2022 to 2025) puts even the big cities well under one a year, and much of the country at none. Central London leads, at around half a tropical night a year over that window. Birmingham and Manchester each recorded about one across four summers. Edinburgh, Cardiff and rural areas sat at zero.
That count understates the warmest city centres, for reasons covered below, but the headline holds. Today a true tropical night is a rare event almost everywhere in Britain. Central London has had them - parts of the capital stayed above 20°C overnight during the July 2022 heatwave - yet they remain the exception. The Met Office expects tropical nights again across parts of England and Wales during the 24-25 June 2026 heatwave - the same spell forecast to break the UK's June temperature record.
The outlook is what changes. The Met Office's UKCP18 projections, the UK's national climate dataset, show tropical nights climbing as the world warms. These projections run by global warming level rather than by calendar year. The world has already warmed by more than 1°C since pre-industrial times, and current policies point towards roughly 2.4°C to 2.8°C, depending on future emissions.
The projected count climbs steeply for the warmest cities. Taking the central (median) estimate from the Met Office Annual Count of Tropical Nights:
| City | Recent (modelled baseline) | At 2°C warming | At 4°C warming | |---|---|---|---| | London | ~1 | ~3 | ~15 | | Brighton | under 1 | under 1 | ~8 | | Bristol | under 1 | under 1 | ~7 | | Cardiff | under 1 | under 1 | ~7 | | Liverpool | under 1 | under 1 | ~6 | | Manchester | under 1 | under 1 | ~5 | | Cambridge | under 1 | under 1 | ~4 | | Birmingham | under 1 | under 1 | ~3 | | Leeds | under 1 | under 1 | ~2 | | Newcastle | under 1 | under 1 | ~1 | | Edinburgh | under 1 | under 1 | ~1 |
_Source: Met Office UKCP18, Annual Count of Tropical Nights (12km, high-emissions RCP8.5 scenario, central estimate). Figures describe the wider area around each city._
The "recent" column is the UKCP18 model's own baseline, included so the projected rows have a like-for-like comparison; it sits close to the observed ERA5 figures above (both put London at about one a year or fewer today).
Read across the rows and the split stands out. At 2°C of warming, the level current policies put the world roughly on track to pass around mid-century, only London sees tropical nights with any regularity, at about three a year. Every other city stays below one. The numbers reach the mid to high single figures for southern and coastal cities only at the high-end 4°C level, well beyond the current-policy path, and about fifteen for the capital.
Treat these as probabilities, not forecasts. The figures are central estimates from a wide range of model outcomes, and a lower-emissions world produces lower numbers. No single year is promised to match them.
Tropical nights cluster where a warm regional climate meets something that holds heat overnight. London and the South East get the warmest summers, and dense city centres add the urban heat island, where buildings and paved surfaces give back the day's stored heat slowly after dark. The capital leads every projection as a result.
The coast plays a quieter role. Across all 361 UK council areas, some of the highest counts at higher warming levels land not in the biggest cities but on the warm southern and eastern shore. Coastal Kent, around Margate and the Thanet peninsula, tops the council figures at 4°C. The sea is the reason. Water warms and cools far more slowly than land, so on a hot night it keeps coastal air from dropping as far as it would inland, and a warm seaside town can hold a tropical night that a town a few miles inland loses.
The North of England, Wales beyond the Cardiff area, Scotland and Northern Ireland sit close to zero throughout, with only a handful of tropical nights showing even at the highest warming levels. Across upland and northern Britain the cool maritime climate keeps overnight temperatures under the threshold.
Tropical nights bite hardest in the homes least able to lose heat. Top-floor flats, homes with windows on one side only, and well-insulated buildings without a way to ventilate all trap warmth overnight, and a run of warm nights in a heatwave, not one hot afternoon, is what turns a home uncomfortable and, for vulnerable people, risky. Older adults, young children, and anyone with a heart or respiratory condition feel it first.
This is context, not a warning. Tropical nights stay rare across most of the UK, and the projections keep them rare for years outside London and the warm coast. For anyone weighing up a city-centre flat or a warm southern town, overnight cooling - which way the rooms face, whether air moves through, what shade there is - earns a moment's thought it would not have a generation ago.
Two things keep the numbers honest.
Start with resolution. The Met Office publishes these projections on a 12km grid. That suits a wider-area figure, but a single cell blends a dense core with its greener edges, so the count understates the hottest, most built-up centres. Central London runs higher than its grid cell shows.
Then framing. The figures track global warming levels rather than dates, and they come from the high-emissions scenario inside UKCP18. The central estimate sits in the middle of a wide range, not at the end of a forecast, and a lower-emissions world lands lower. We frame by warming level on purpose: for a metric whose timing rests on choices the world has not yet made, that is the straight way to show it.
LocalRisk shows the projected tropical-nights figure next to the hot-days projection in the heat section of every postcode, council and area report, so you can see where your part of the country sits. The heat risk guide covers the wider context: what the projections mean, and how the urban heat island and overheating in homes fit together.
_Tropical-night projections: Met Office UKCP18 Annual Count of Tropical Nights (12km, RCP8.5, central estimate), Open Government Licence v3.0. Recent observed figures: ERA5 reanalysis (ECMWF) via Open-Meteo, 2022 to 2025. Coastal council figures reflect 12km grid cells that include open sea, which keeps overnight temperatures higher._