Tropical nights come to Europe

The biggest rise in extreme tem per at ures is not in the day time. Night-time heat is harder to mit ig ate, with increas -ingly severe con sequences for health and eco nomic reper cus sions set to get worse.

Financial Times Europe11 Jul 2026By Attracta Mooney, Nas sos Styl i anou and Jana Tausch in ski

As Lorna Pow ell, an NHS urgent care doc tor in Lon don, watched a weather fore castfor extreme heat across the UK in June, one pre dic tion in par tic u lar caught heratten tion. Met eor o lo gists warned that the Brit ish cap ital could exper i ence a slew ofso-called trop ical nights, in which tem per at ures remain above 20C. The pre dic tioncame true: last month Lon don endured a record-equalling five con sec ut ive suchnights. For Pow ell, that meant more patients.

The UK is far from alone as cli mate change drives more extreme weather.

Across the world, the hot test nights are warm ing at a faster rate than the hot testdays — with increas ingly severe con sequences for health and eco nomic reper cus -sions also set to get worse.Much of Europe has just exper i enced the most swel ter ing June on record, with hun -dreds of weather sta tions in at least 15 coun tries report ing their hot test nights ever,FT ana lysis of pro vi sional tem per at ure data shows.

“What stands out about June’s heat wave is not only the day time intens ity but theextraordin ary warmth overnight,” says Robert Rohde, lead sci ent ist at Berke leyEarth, a US non-profit cli mate research organ isa tion.

More than half the long stand ing mon it or ing sites across Ger many, France and theUK registered their warmest June night on record, many smash ing pre vi ous highsby sev eral degrees. In Kubschütz, just east of Dresden in Ger many, the mer cury didnot dip below 29.4C on June 27, set ting a new national record for the coun try’swarmest night.

Night-time heat is harder to mit ig ate than its day time equi val ent, while its healtheffects can be dev ast at ing.

“If the night does not cool down, the body loses its main oppor tun ity to recover,”says Dominic Royé, a cli mate sci ent ist who has examined the impact of hot nightsacross 44 coun tries and is affil i ated with the Bio lo gical Mis sion of Galicia, a Span ishresearch insti tu tion. “Unusu ally warm nights have their own inde pend ent impacton mor tal ity.”

Since the body relies on a tem per at ure drop of about 1C to ini ti ate deep sleep, trop -ical nights can deny people rest. While heart beats and blood pres sure nor mally falldur ing sleep, on a hot night the heart is forced to pump twice the nor mal volume ofblood to cool down the body. The heat and addi tional strain lead to excess sweat ingand poten tial dehyd ra tion.

“Dur ing the June heat wave, we struggled to keep pace with the sharp rise in life-threat en ing ill nesses triggered by dan ger ously high tem per at ures, par tic u larlyovernight,” says Pow ell, the NHS doc tor who also helps lead Moth ers Rise Up, a cli -mate action group.

In Europe and other parts of the world where domestic air con di tion ing is a rar ity,there is also an eco nomic cost. “That under ly ing night-time heat stress on the bodyis cost ing money,” says Kathy Baugh man McLeod, chief exec ut ive of Hera, a non-profit focus ing on cli mate adapt a tion. “People go to work, their hand-eye co-ordin a -tion is off, they make mis takes, they hurt them selves, they hurt other people.”

Parts of Asia, includ ing China, Iran and Saudi Ara bia, have also exper i enced sig ni -fic ant increases in overnight tem per at ures. But across the world’s 500 most pop u -lous cit ies, FT ana lysis of data from the EU’s Coper ni cus Cli mate Change Ser viceshows, the sharpest rises in night-time tem per at ures have been con cen trated insouth ern and east ern Europe. Night-time tem per at ures rep res ent the min imumacross a 24hour period, typ ic ally reached before sun rise.In some European cit ies, the hot test nights have warmed by more than 0.5C per dec -ade, more than twice the aver age increase across all loc a tions ana lysed.

Mark McCarthy, a sci ence man ager at the UK’s Met Office, says that his tor ic ally,trop ical nights were very rare for much of the con tin ent.

“What we’re see ing is that [hot nights are] increas ingly fre quent,” he adds. “And ourcli mate pro jec tions sug gest that that’s a trend that we would expect to con tinue.”

Research pub lished last month in Nature Cli mate Change, a sci entific journal, foundthat the 10 hot test nights of each year have warmed faster than the 10 hot test days— by a global aver age of 0.32C per dec ade com pared with 0.27C per dec ade, respect -ively.

The study also found that dur ing one in 10 trop ical nights people are now hit by“heat stress”, when humid ity and other factors add to dis com fort, up from aboutone in 30 in the 1970s.

Sep ar ately, when a very hot day is fol lowed by a trop ical night, the human body haslittle oppor tun ity to recover. In Europe, occur rences of a so-called heat stress dayfol lowed by a trop ical night have increased by 73 per cent since the 1970s. “It’s notjust a future prob lem,” says Rebecca Emer ton, a sci ent ist at the European Centre forMedium-Range Weather Fore casts and the study’s lead author. “This has alreadyhappened.”

In Bri tain, a YouGov sur vey com mis sioned by Green peace UK found that two-thirdsof adults struggled to sleep dur ing June’s heat wave, with about half say ing they lostthree or more hours of sleep each night. Another study estim ated the costs of tem -per at ure-caused sleep loss at about 0.04 per cent of GDP per year — or just over£1bn.

Such fig ures are only likely to increase. Patrick Bigler of the Uni versity of Lausannehas sug ges ted hot nights could increase five fold by the end of the cen tury, based ona cli mate change scen ario in which emis sions peak by around 2040 and thendecline.

High night-time tem per at ures have also been linked to a rise in domestic viol enceand crime, says Baugh man McLeod. People are “irrit able, frus trated, can’t get com -fort able, and want to take it out on some body”, she says.

Then there are the health chal lenges. Those with under ly ing prob lems, the eld erlyand the very young are espe cially vul ner able. The risk of strokes increases by 7 percent dur ing trop ical nights, a 2024 study found, while there are also higherinstances of men tal dis turb ances com pared with hot days.

After the June heat wave, Ger many recor ded almost 5,500 excess deaths, accord ingto pro vi sional data. France registered 2,000 and Bel gium 1,200. Mad rid’s Car los IIIHealth Insti tute repor ted at least 1,028 heat-related deaths in Spain.

One of the biggest issues is that night time “adapt a tion options are more lim itedthan dur ing the day”, Royé says. “Dur ing the day, people can seek shade, reduceactiv ity or enter an air-con di tioned build ing,” he adds. “At night, open ing win dows,the most basic and access ible strategy, stops work ing when it is just as hot out sideas it is inside.”

Air con di tion ing is more effect ive in redu cing heat than such ele ment ary responsesand the Inter na tional Energy Agency expects the num ber of air con di tion ersinstalled across the EU to more than double from about 130mn in 2023 to 275mn by2050. But the devices can increase the tem per at ure in neigh bour ing houses, areoften expens ive to run and, even when fuelled by clean energy, increase the green -house gas emis sions that con trib ute to cli mate change.

Pow ell, the NHS doc tor at Moth ers Rise Up, says ulti mately coun tries need to cutemis sions. In the mean time, “vul ner able people need to under stand the healthrisks, try to stay well hydrated and cool one room in their home if pos sible”, sheadvises. With Lon don swel ter ing through its third heat wave in less than twomonths — and record ing another trop ical night on Thursday — she is feel ing onedge.

“As the hot nights just keep on com ing, I brace myself before every shift, know ingwe are going to be inund ated with heat-exhausted babies and a spike in urgent