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Rome · September · relief from the heat

Coolest places to go from Rome in September

The coolest place you can reach from Rome in September within 15 hours is Reykjavik, 14.8 °C cooler, costing 830 kg CO₂e return. The lowest-carbon option is Città di Castello at 5.2 kg — 160× less carbon, for 12.4 degrees less relief from the heat.

The 10 coolest places within 15 hours of Rome

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, Iceland14.8 °C cooler · 6.3 h sun a dayair 7h 54m · 830 kg CO₂e return
  2. Tromsø, Norway12.6 °C cooler · 4.9 h sun a dayair 7h 36m · 782 kg CO₂e return
  3. Östersund, Sweden11.6 °C cooler · 7.7 h sun a dayair 6h 42m · 596 kg CO₂e return
  4. Bodø, Norway11.4 °C cooler · 5.2 h sun a dayair 7h 18m · 711 kg CO₂e return
  5. Rovaniemi, Finland11.1 °C cooler · 6.0 h sun a dayair 7h 18m · 718 kg CO₂e return
  6. Trondheim, Norway10.5 °C cooler · 7.0 h sun a dayair 6h 42m · 603 kg CO₂e return
  7. Sundsvall, Sweden10.0 °C cooler · 8.4 h sun a dayair 6h 36m · 579 kg CO₂e return
  8. Luleå, Sweden10.0 °C cooler · 7.7 h sun a dayair 7h 6m · 680 kg CO₂e return
  9. Dundee, United Kingdom9.9 °C cooler · 7.7 h sun a dayair 6h 6m · 494 kg CO₂e return
  10. Glasgow, United Kingdom9.3 °C cooler · 7.2 h sun a dayair 6h 6m · 495 kg CO₂e return

Without flying

The coolest places the train reaches within 15 hours. La Chaux-de-Fonds is 8.2 °C cooler for 21.6 kg — about 38× less carbon than flying to Reykjavik.

  1. La Chaux-de-Fonds, Switzerland8.2 °C cooler · 9.2 h sun a dayrail 9h 12m · 21.6 kg CO₂e return
  2. Memmingen, Germany7.3 °C cooler · 9.6 h sun a dayrail 9h 42m · 20.7 kg CO₂e return
  3. Bern, Switzerland6.9 °C cooler · 9.6 h sun a dayrail 8h 36m · 20.4 kg CO₂e return
  4. Ulm, Germany6.6 °C cooler · 9.7 h sun a dayrail 10h 18m · 22.1 kg CO₂e return
  5. Munich, Germany6.6 °C cooler · 9.1 h sun a dayrail 10h 30m · 20.6 kg CO₂e return
  6. Augsburg, Germany6.3 °C cooler · 9.5 h sun a dayrail 10h 30m · 21.6 kg CO₂e return

Rail times are modelled; air times include getting to and through the airport.

The low-carbon trade-off

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.

Città di CastelloReykjavik
Where they are. Solid lines are rail or ferry, dashed are flights, from Rome. Pick one to compare.
Carbon against relief from the heat, September, departing Rome. Journeys of up to 15 hours each way.10 destinations. Lowest carbon Città di Castello at 5.2 kilograms and 2.4 °C cooler; best for relief from the heat Reykjavik at 830 kilograms and 14.8 °C cooler. Città di Castello · 5.2 kgSonthofen · 19.2 kgBuxton · 417 kgReykjavik · 830 kg

By rail or ferry By air

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

What the 15-hour limit costs: at this budget Buxton can only be reached by air — 417 kg CO₂e, in 5h 42m. Allow up to 24 hours and the train does the same journey for 60.8 kg in 21h — 7× less carbon for 15h 18m more travelling.

September from Rome — 10 destinations on the frontier, 5 without flying.
DestinationHowCO₂e returnTempSun/dayRain/dayJourney
Città di Castello, ItalyRail5.2 kg19.9 °C10.2 h3.1 mm4h
Campobasso, ItalyRail5.4 kg18.4 °C10.2 h1.9 mm4h 12m
Ljubljana, SloveniaRail14.4 kg17.0 °C9.6 h4.1 mm9h
Klagenfurt, AustriaRail16.1 kg16.1 °C9.3 h3.9 mm9h 18m
Sonthofen, GermanyRail19.2 kg14.5 °C9.0 h5.3 mm9h
Buxton, United KingdomAir417 kg12.8 °C7.1 h3.9 mm5h 42m
Bergen, NorwayAir532 kg12.1 °C6.5 h8.8 mm6h 18m
Östersund, SwedenAir596 kg10.7 °C7.7 h2.6 mm6h 42m
Tromsø, NorwayAir782 kg9.7 °C4.9 h5.2 mm7h 36m
Reykjavik, IcelandAir830 kg7.5 °C6.3 h3.5 mm7h 54m

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 Sonthofen (19.2 kg, 7.8 °C cooler) to Buxton (417 kg, 9.5 °C cooler) buys 1.7 °C more relief from the heat for an extra 398 kg — 234 kg of CO₂e per degree. That single step is the most expensive relief from the heat on the whole curve.

The pick of them

Città di CastelloItaly5.2 kg CO₂e return19.9 °C · 10.2 h sun · 4h by railwarm but wetSonthofenGermany19.2 kg CO₂e return14.5 °C · 9.0 h sun · 9h by railmild and brightReykjavik, IcelandReykjavikIceland830 kg CO₂e return7.5 °C · 6.3 h sun · 7h 54m 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 Rome

September from elsewhere

Photo credits

Questions

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

Reykjavik, Iceland, at 14.8 °C cooler. Reaching it emits 830 kg CO₂e return, travelling 7h 54m each way by air (modelled).

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

Yes. Sonthofen reaches 7.8 °C cooler and is reachable by rail or ferry in 9h (modelled), emitting 19.2 kg CO₂e return — though Reykjavik is cooler still, if you fly.

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

830 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.