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London · September · relief from the heat

Coolest places to go from London in September

In September, the coolest well-known place within 15 hours of London is Reykjavik, Iceland, 9.1 °C cooler than London and 6.3 h sun a day, about 6h each way by air. Without flying, it is Dundee, United Kingdom, 4.2 °C cooler than London, about 7h 18m each way by train, for about 10× less carbon (46.8 kg CO₂e return against 475 kg).

The 10 coolest places within 15 hours of London

Ranked on relief from the heat in September alone, among well-known places (a Wikivoyage travel guide and at least 40,000 Wikipedia readers a year), one per area and at most three per country. The carbon is shown, not used to choose: the list further down is the other question, how much relief from the heat each extra kilogram buys.

  1. Reykjavik, Iceland9.1 °C cooler · 6.3 h sun a day · 3.5 mm rain a day · sea 10.8 °Cair ≈ 6h · 475 kg CO₂e return
  2. Tromsø, Norway6.9 °C cooler · 4.9 h sun a day · 5.2 mm rain a dayair ≈ 6h 30m · 565 kg CO₂e return
  3. Östersund, Sweden5.9 °C cooler · 7.7 h sun a day · 2.6 mm rain a dayair ≈ 5h 36m · 393 kg CO₂e return
  4. Bodø, Norway5.7 °C cooler · 5.2 h sun a day · 6.6 mm rain a day · sea 13.0 °Cair ≈ 6h 6m · 484 kg CO₂e return
  5. Rovaniemi, Finland5.4 °C cooler · 6.0 h sun a day · 3.5 mm rain a dayair ≈ 6h 24m · 552 kg CO₂e return
  6. Trondheim, Norway4.8 °C cooler · 7.0 h sun a day · 5.8 mm rain a dayair ≈ 5h 30m · 368 kg CO₂e return
  7. Sundsvall, Sweden4.3 °C cooler · 8.4 h sun a day · 2.3 mm rain a day · sea 14.2 °Cair ≈ 5h 36m · 402 kg CO₂e return
  8. Luleå, Sweden4.3 °C cooler · 7.7 h sun a day · 2.4 mm rain a day · sea 14.3 °Cair ≈ 6h 12m · 505 kg CO₂e return
  9. Dundee, United Kingdom4.2 °C cooler · 7.7 h sun a day · 2.0 mm rain a day · sea 13.9 °Crail ≈ 7h 18m · 46.8 kg CO₂e return
  10. Glasgow, United Kingdom3.6 °C cooler · 7.2 h sun a day · 3.4 mm rain a dayrail ≈ 6h · 44.6 kg CO₂e return

Without flying

The coolest places the train reaches within 15 hours. Dundee is 4.2 °C cooler for 46.8 kg — about 10× less carbon than flying to Reykjavik.

  1. Dundee, United Kingdom4.2 °C cooler · 7.7 h sun a day · 2.0 mm rain a day · sea 13.9 °Crail ≈ 7h 18m · 46.8 kg CO₂e return
  2. Inverness, United Kingdom4.1 °C cooler · 7.3 h sun a day · 2.9 mm rain a dayrail ≈ 9h 6m · 57.4 kg CO₂e return
  3. Aberdeen, United Kingdom3.8 °C cooler · 8.4 h sun a day · 1.6 mm rain a day · sea 13.4 °Crail ≈ 8h 30m · 51.4 kg CO₂e return
  4. Glasgow, United Kingdom3.6 °C cooler · 7.2 h sun a day · 3.4 mm rain a dayrail ≈ 6h · 44.6 kg CO₂e return
  5. La Chaux-de-Fonds, Switzerland2.5 °C cooler · 9.2 h sun a day · 3.5 mm rain a dayrail ≈ 10h 30m · 20.7 kg CO₂e return

≈ is the model's estimate (air times include getting to and through the airport); ✓ is a rail journey checked against a real timetable, with the date it was checked. Temperatures are historical daily means for 2023–2024, averaged across day and night, so afternoons run warmer.

The low-carbon trade-off

The coolest place you can reach from London in September within 15 hours is Reykjavik, 9.1 °C cooler, costing 475 kg CO₂e return. The lowest-carbon option is Mansfield at 15.7 kg — 30× less carbon, for 7.1 degrees less relief from the heat.

Every destination here is on the efficiency frontier: nowhere else this site covers is both cooler in September and lower in carbon. Anything a better option beats outright has been left out.

MansfieldReykjavik
Where they are. Solid lines are rail or ferry, dashed are flights, from London. Pick one to compare.
Carbon against relief from the heat, September, departing London. Journeys of up to 15 hours each way.6 destinations. Lowest carbon Mansfield at 15.7 kilograms and 2.0 °C cooler; best for relief from the heat Reykjavik at 475 kilograms and 9.1 °C cooler. Mansfield · 15.7 kgStirling · 45.8 kgKristiansund · 345 kgReykjavik · 475 kg

By rail or ferry By air

Carbon against relief from the heat, September, departing London. Journeys of up to 15 hours each way.
September from London — 6 destinations on the frontier, 3 without flying.
DestinationHowCO₂e returnTempSun/dayRain/dayJourney
Mansfield, United KingdomRail15.7 kg14.6 °C7.3 h3.4 mm4h 6m
Buxton, United KingdomRail18.4 kg12.8 °C7.1 h3.9 mm4h 36m
Stirling, United KingdomRail45.8 kg12.3 °C7.2 h3.3 mm7h 6m
Kristiansund, NorwayAir345 kg11.6 °C7.1 h6.5 mm5h 18m
Östersund, SwedenAir393 kg10.7 °C7.7 h2.6 mm5h 36m
Reykjavik, IcelandAir475 kg7.5 °C6.3 h3.5 mm6h

The flights, in practice

The model measures to the town, not to a runway. For the destinations above reached by air, this is the nearest airport, how far it is, and whether a direct flight from London is listed on the airport's own destination page (researched 2026-09-15; route existence, not availability on a date). "Not checked" means no destination list was read for that airport.

Airports for the air destinations on this frontier, checked 2026-09-15.
DestinationAirportFrom townDirect from LondonOnward
Kristiansund, NorwayKristiansund Kvernberget KSU7 kmnoLocal bus or taxi to Kristiansund.
Östersund, SwedenÅre Östersund OSD11 kmnoAirport bus or taxi to Östersund.
Reykjavik, IcelandKeflavík International KEF50 kmyes LHR, LGW, STN, LTNAirport coach or public bus to Reykjavík; KEF is used instead of the domestic city airport.
Sources for this table

Warm is not the same as pleasant, which is why sunshine and rainfall are shown alongside temperature. All three are ERA5 monthly means for 2023–2024.

Where the curve breaks

The frontier is gentle until it isn't. Going from Stirling (45.8 kg, 4.3 °C cooler) to Kristiansund (345 kg, 5.0 °C cooler) buys 0.7 °C more relief from the heat for an extra 299 kg — 427 kg of CO₂e per degree. That single step is the most expensive relief from the heat on the whole curve.

The pick of them

Mansfield, United KingdomMansfieldUnited Kingdom15.7 kg CO₂e return14.6 °C · 7.3 h sun · 4h 6m by railmild and brightStirling, United KingdomStirlingUnited Kingdom45.8 kg CO₂e return12.3 °C · 7.2 h sun · 7h 6m by railmild and brightReykjavik, IcelandReykjavikIceland475 kg CO₂e return7.5 °C · 6.3 h sun · 6h by aircool

The same month, asked differently

September answers differently depending on what you are after, and the lists genuinely diverge: the brightest places are not the hottest, and in summer the useful question stops being where is warm at all.

Where to stay in Reykjavik

Places to stay in Reykjavik, Iceland, on a live map. Prices and availability come from Stay22 and its booking partners.

Search places to stay in Reykjavik →Opens the booking search in a new tab. Same partners as the map below.

Affiliate disclosure. A booking made through this map may earn 0xCarbon a commission, at no extra cost to you. It changes nothing above it: the emissions figures come from UK Government conversion factors and are computed before anyone is paid anything.See the method.

Other months from London

September from elsewhere

Photo credits

Questions

Where is the coolest place to go from London in September?

Reykjavik, Iceland, at 9.1 °C cooler. Reaching it emits 475 kg CO₂e return, travelling 6h each way by air (modelled).

Can I get somewhere cool from London in September without flying?

Yes. Stirling reaches 4.3 °C cooler and is reachable by rail or ferry in 7h 6m (modelled), emitting 45.8 kg CO₂e return — though Reykjavik is cooler still, if you fly.

How much carbon does a return trip from London to Reykjavik produce?

475 kg CO₂e for one person, return, by air. That uses the UK Government's 2026 conversion factors, including radiative forcing for flights.

Carbon uses UK Government (DESNZ/DEFRA) 2026 conversion factors applied to great-circle distance, with radiative forcing included for flights. Rail journey times are modelled estimates, not timetabled services. Full method · download the data.