Key takeaways
- Central London had about 5 days a year above 30°C in the 2001 to 2020 climate; at 2.5°C of global warming the Met Office projects about 13.
- The north starts from a much lower base: Newcastle upon Tyne sees fewer than one such days a year now and about one at 2.5°C of warming.
- The Met Office says current international commitments point to a world roughly 2.4°C to 2.8°C warmer than pre-industrial.
- In central London, days above 30°C rise by about 160% at 2.5°C of warming, and cooling degree days, a guide to how long cooling would run, by about 66% (80 to 133).
The UK hit 40°C for the first time in July 2022. It is easy to treat that as a freak, but the Met Office’s projections suggest the days either side of it, the ones in the low thirties that make homes uncomfortable and nights hard to sleep through, are the bigger story. And they differ a lot by where you live.
The figures below come from the Met Office Climate Data Portal, which publishes the UKCP18 projections averaged over every local authority. Rather than tie them to a year, the Met Office reports them for global warming levels: how much warmer the world is than before industrialisation. It notes that current international agreements point to somewhere around 2.4°C to 2.8°C, so we use 2.5°C as the central case.
Days above 30°C, area by area
| Area | 1981-2000 | 2001-2020 | At +2°C | At +2.5°C | At +4°C |
|---|---|---|---|---|---|
| Westminster | 2 | 5 | 11 | 13 | 30 |
| Cambridge | 2 | 6 | 11 | 13 | 29 |
| Reading | 2 | 4 | 8 | 12 | 27 |
| Southampton | 1 | 3 | 7 | 11 | 25 |
| Birmingham | 1 | 3 | 5 | 7 | 19 |
| Bristol | 1 | 3 | 4 | 7 | 20 |
| Norwich | 1 | 2 | 5 | 7 | 17 |
| Manchester | 0 | 2 | 3 | 4 | 13 |
| Leeds | 0 | 1 | 2 | 4 | 12 |
| Liverpool | 0 | 1 | 2 | 3 | 10 |
| Newcastle upon Tyne | 0 | 0 | 1 | 1 | 4 |
- 1981-20002
- 2001-20205
- At +2°C11
- At +2.5°C13
- At +3°C18
- At +4°C30
Source: Met Office UKCP18 local-authority projections (median). OGL v3.0.
Why the south and east lead
The projections show warming rising from the north-west towards the south-east. London, the Thames Valley and East Anglia start warmer, sit further from the cooling influence of the Atlantic, and gain the most hot days. Big cities add an urban heat island on top, because dense streets store heat and give it back at night.
The number that matters for sleep: warm nights
A tropical night is one that stays above 20°C. They are rare now, but in Westminster they rise from about 1 a year to about 4 at 2.5°C of warming and about 15 at 4°C. On those nights opening the window cannot cool a bedroom, because the outside air is not cool.
What it means for cooling demand
Cooling degree days add up how far, and how often, the daily mean temperature sits above 22°C, which makes them a good guide to how many hours a cooling system would run. In Westminster they go from about 80 a year to about 133 at 2.5°C of warming, a rise of about 66%. Days above 30°C rise by about 160% over the same step, from a lower base, so the hottest days multiply while the overall cooling load grows more steadily. The cost of running a unit for an hour does not change, but the number of hours you need it does.
Free toolFuture summersHow hot your area is set to getWhere you live sets the climate. Your home sets how much of it gets indoors. The Home Cooling Checker combines both.
Frequently asked questions
How many days above 30°C does London get?
About 5 a year in the 2001 to 2020 climate, on the Met Office's local projections for central London, rising to about 13 in a world 2.5°C warmer than pre-industrial.
Which part of the UK will get hottest?
London, the South East and East of England gain the most hot days in the Met Office projections. Of the areas in our table, the north of England gains the fewest: Newcastle upon Tyne goes from fewer than one to about one a year at 2.5°C.
What is a global warming level?
How much warmer the world is than in the pre-industrial period of 1850 to 1900. The Met Office reports its local projections by warming level rather than by year.
Sources
Solomon Amos, Founder & Technical Architect, GetComfort
Solomon Amos is the founder and technical architect of GetComfort, and built HomePortfolio, the property-intelligence platform behind this site's property data. He is not an installer: every accreditation and planning claim here is sourced to its primary guidance, as the methodology sets out. More about the author
