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Madrid · September · relief from the heat

Coolest places to go from Madrid in September

In September, the coolest well-known place within 15 hours of Madrid is Reykjavik, Iceland, 12.2 °C cooler than Madrid and 6.3 h sun a day, about 7h 24m each way by air. Without flying, it is La Chaux-de-Fonds, Switzerland, 5.6 °C cooler than Madrid, about 14h 18m each way by train, for about 22× less carbon (33.2 kg CO₂e return against 727 kg).

The 10 coolest places within 15 hours of Madrid

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, Iceland12.2 °C cooler · 6.3 h sun a day · 3.5 mm rain a day · sea 10.8 °Cair ≈ 7h 24m · 727 kg CO₂e return
  2. Tromsø, Norway10.0 °C cooler · 4.9 h sun a day · 5.2 mm rain a dayair ≈ 8h 12m · 882 kg CO₂e return
  3. Östersund, Sweden9.0 °C cooler · 7.7 h sun a day · 2.6 mm rain a dayair ≈ 7h 12m · 705 kg CO₂e return
  4. Bodø, Norway8.8 °C cooler · 5.2 h sun a day · 6.6 mm rain a day · sea 13.0 °Cair ≈ 7h 42m · 801 kg CO₂e return
  5. Rovaniemi, Finland8.5 °C cooler · 6.0 h sun a day · 3.5 mm rain a dayair ≈ 8h 6m · 861 kg CO₂e return
  6. Trondheim, Norway7.9 °C cooler · 7.0 h sun a day · 5.8 mm rain a dayair ≈ 7h 6m · 685 kg CO₂e return
  7. Sundsvall, Sweden7.4 °C cooler · 8.4 h sun a day · 2.3 mm rain a day · sea 14.2 °Cair ≈ 7h 18m · 708 kg CO₂e return
  8. Luleå, Sweden7.4 °C cooler · 7.7 h sun a day · 2.4 mm rain a day · sea 14.3 °Cair ≈ 7h 48m · 815 kg CO₂e return
  9. Dundee, United Kingdom7.3 °C cooler · 7.7 h sun a day · 2.0 mm rain a day · sea 13.9 °Cair ≈ 5h 54m · 449 kg CO₂e return
  10. Glasgow, United Kingdom6.7 °C cooler · 7.2 h sun a day · 3.4 mm rain a dayair ≈ 5h 48m · 432 kg CO₂e return

Without flying

The coolest places the train reaches within 15 hours. La Chaux-de-Fonds is 5.6 °C cooler for 33.2 kg — about 22× less carbon than flying to Reykjavik.

  1. La Chaux-de-Fonds, Switzerland5.6 °C cooler · 9.2 h sun a day · 3.5 mm rain a dayrail ≈ 14h 18m · 33.2 kg CO₂e return
  2. Bern, Switzerland4.3 °C cooler · 9.6 h sun a day · 3.6 mm rain a dayrail ≈ 14h 36m · 34.0 kg CO₂e return
  3. Andorra la Vella, Andorra4.0 °C cooler · 10.1 h sun a day · 1.9 mm rain a dayrail ≈ 7h 6m · 14.6 kg CO₂e return
  4. Lugo, Spain3.7 °C cooler · 9.4 h sun a day · 4.2 mm rain a dayrail ≈ 6h 36m · 12.7 kg CO₂e return
  5. Brest, France3.3 °C cooler · 9.1 h sun a day · 3.7 mm rain a day · sea 15.5 °Crail ≈ 14h 6m · 26.2 kg CO₂e return
  6. Quimper, France3.2 °C cooler · 9.1 h sun a day · 2.7 mm rain a day · sea 17.4 °Crail ≈ 13h 36m · 24.9 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 Madrid in September within 15 hours is Reykjavik, 12.2 °C cooler, costing 727 kg CO₂e return. The lowest-carbon option is Salamanca at 5.2 kg — 140× less carbon, for 9.8 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.

SalamancaReykjavik
Where they are. Solid lines are rail or ferry, dashed are flights, from Madrid. Pick one to compare.
Carbon against relief from the heat, September, departing Madrid. Journeys of up to 15 hours each way.8 destinations. Lowest carbon Salamanca at 5.2 kilograms and 2.4 °C cooler; best for relief from the heat Reykjavik at 727 kilograms and 12.2 °C cooler. Salamanca · 5.2 kgLa Chaux-de-Fonds · 33.2 kgEbbw Vale · 318 kgReykjavik · 727 kg

By rail or ferry By air

Carbon against relief from the heat, September, departing Madrid. Journeys of up to 15 hours each way.

What the 15-hour limit costs: at this budget Stirling can only be reached by air — 439 kg CO₂e, in 5h 48m. Allow up to 24 hours and the train does the same journey for 83.1 kg in 23h 6m — 5× less carbon for 17h 18m more travelling.

September from Madrid — 8 destinations on the frontier, 3 without flying.
DestinationHowCO₂e returnTempSun/dayRain/dayJourney
Salamanca, SpainRail5.2 kg17.3 °C10.5 h1.3 mm4h 6m
Soria, SpainRail5.4 kg15.3 °C10.1 h2.3 mm4h 6m
La Chaux-de-Fonds, SwitzerlandRail33.2 kg14.1 °C9.2 h3.5 mm14h 18m
Ebbw Vale, United KingdomAir318 kg13.3 °C6.9 h5.6 mm5h 12m
Stirling, United KingdomAir439 kg12.3 °C7.2 h3.3 mm5h 48m
Kristiansund, NorwayAir663 kg11.6 °C7.1 h6.5 mm7h
Östersund, SwedenAir705 kg10.7 °C7.7 h2.6 mm7h 12m
Reykjavik, IcelandAir727 kg7.5 °C6.3 h3.5 mm7h 24m

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 La Chaux-de-Fonds (33.2 kg, 5.6 °C cooler) to Ebbw Vale (318 kg, 6.4 °C cooler) buys 0.8 °C more relief from the heat for an extra 285 kg — 356 kg of CO₂e per degree. That single step is the most expensive relief from the heat on the whole curve.

The pick of them

Salamanca, SpainSalamancaSpain5.2 kg CO₂e return17.3 °C · 10.5 h sun · 4h 6m by railwarm overallLa Chaux-de-FondsSwitzerland33.2 kg CO₂e return14.1 °C · 9.2 h sun · 14h 18m by railmild and brightReykjavik, IcelandReykjavikIceland727 kg CO₂e return7.5 °C · 6.3 h sun · 7h 24m 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 Madrid

September from elsewhere

Photo credits

Questions

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

Reykjavik, Iceland, at 12.2 °C cooler. Reaching it emits 727 kg CO₂e return, travelling 7h 24m each way by air (modelled).

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

Yes. La Chaux-de-Fonds reaches 5.6 °C cooler and is reachable by rail or ferry in 14h 18m (modelled), emitting 33.2 kg CO₂e return — though Reykjavik is cooler still, if you fly.

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

727 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.