Lisbon · September · relief from the heat

Coolest places to go from Lisbon in September

In September, the coolest well-known place within 15 hours of Lisbon is Reykjavik, Iceland, 13.2 °C cooler than Lisbon and 6.3 h sun a day, about 7h 24m each way by air. Without flying, it is Ávila, Spain, 4.9 °C cooler than Lisbon, about 8h 18m each way by train, for about 57× less carbon (12.9 kg CO₂e return against 741 kg).

The 10 coolest places within 15 hours of Lisbon

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.

Reykjavik, Iceland13.2 °C cooler · 6.3 h sun a day · 3.5 mm rain a day · sea 10.8 °Cair ≈ 7h 24m · 741 kg CO₂e return
Tromsø, Norway11.0 °C cooler · 4.9 h sun a day · 5.2 mm rain a dayair ≈ 8h 36m · 893 kg CO₂e return
Östersund, Sweden10.0 °C cooler · 7.7 h sun a day · 2.6 mm rain a dayair ≈ 7h 42m · 792 kg CO₂e return
Bodø, Norway9.8 °C cooler · 5.2 h sun a day · 6.6 mm rain a day · sea 13.0 °Cair ≈ 8h 12m · 879 kg CO₂e return
Rovaniemi, Finland9.5 °C cooler · 6.0 h sun a day · 3.5 mm rain a dayair ≈ 8h 30m · 885 kg CO₂e return
Trondheim, Norway8.9 °C cooler · 7.0 h sun a day · 5.8 mm rain a dayair ≈ 7h 36m · 764 kg CO₂e return
Sundsvall, Sweden8.4 °C cooler · 8.4 h sun a day · 2.3 mm rain a day · sea 14.2 °Cair ≈ 7h 42m · 800 kg CO₂e return
Luleå, Sweden8.4 °C cooler · 7.7 h sun a day · 2.4 mm rain a day · sea 14.3 °Cair ≈ 8h 18m · 904 kg CO₂e return
Dundee, United Kingdom8.3 °C cooler · 7.7 h sun a day · 2.0 mm rain a day · sea 13.9 °Cair ≈ 6h 12m · 509 kg CO₂e return
Glasgow, United Kingdom7.7 °C cooler · 7.2 h sun a day · 3.4 mm rain a dayair ≈ 6h 6m · 488 kg CO₂e return

Without flying

The coolest places the train reaches within 15 hours. Ávila is 4.9 °C cooler for 12.9 kg — about 57× less carbon than flying to Reykjavik.

Ávila, Spain4.9 °C cooler · 10.8 h sun a day · 2.0 mm rain a dayrail ≈ 8h 18m · 12.9 kg CO₂e return
Lugo, Spain4.7 °C cooler · 9.4 h sun a day · 4.2 mm rain a dayrail ≈ 8h 42m · 14.6 kg CO₂e return
Oviedo, Spain3.9 °C cooler · 9.2 h sun a day · 3.5 mm rain a dayrail ≈ 10h 18m · 17.3 kg CO₂e return
Segovia, Spain3.8 °C cooler · 10.8 h sun a day · 1.2 mm rain a dayrail ≈ 9h 6m · 14.6 kg CO₂e return
Viseu, Portugal2.3 °C cooler · 10.3 h sun a day · 3.1 mm rain a dayrail ≈ 5h · 7.1 kg CO₂e return
Pau, France2.3 °C cooler · 9.4 h sun a day · 3.6 mm rain a dayrail ≈ 14h 54m · 26.4 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 Lisbon in September within 15 hours is Reykjavik, 13.2 °C cooler, costing 741 kg CO₂e return. The lowest-carbon option is Viseu at 7.1 kg — 104× less carbon, for 10.9 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.

Where they are. Solid lines are rail or ferry, dashed are flights, from Lisbon. Pick one to compare.

By rail or ferry By air

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

September from Lisbon — 7 destinations on the frontier, 2 without flying.
Destination	How	CO₂e return	Temp	Sun/day	Rain/day	Journey
Viseu, Portugal	Rail	7.1 kg	18.4 °C	10.3 h	3.1 mm	5h
Guarda, Portugal	Rail	7.6 kg	15.5 °C	10.4 h	2.1 mm	5h 12m
Cork, Ireland	Air	369 kg	14.1 °C	7.1 h	5.2 mm	5h 30m
Ebbw Vale, United Kingdom	Air	383 kg	13.3 °C	6.9 h	5.6 mm	5h 30m
Stirling, United Kingdom	Air	496 kg	12.3 °C	7.2 h	3.3 mm	6h 6m
Kristiansund, Norway	Air	739 kg	11.6 °C	7.1 h	6.5 mm	7h 24m
Reykjavik, Iceland	Air	741 kg	7.5 °C	6.3 h	3.5 mm	7h 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 Stirling (496 kg, 8.4 °C cooler) to Kristiansund (739 kg, 9.1 °C cooler) buys 0.7 °C more relief from the heat for an extra 243 kg — 347 kg of CO₂e per degree. That single step is the most expensive relief from the heat on the whole curve.

The pick of them

ViseuPortugal7.1 kg CO₂e return18.4 °C · 10.3 h sun · 5h by railwarm but wet

GuardaPortugal7.6 kg CO₂e return15.5 °C · 10.4 h sun · 5h 12m by railwarm overall

ReykjavikIceland741 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 Lisbon

September from elsewhere

Photo credits

Viseu: Manuelvbotelho, CC BY-SA 4.0, via Wikimedia Commons
Guarda: Alexa Pinto, CC BY-SA 3.0, via Wikimedia Commons
Reykjavik: Hedwig Storch, CC BY-SA 3.0, via Wikimedia Commons
Tromsø: Diego Delso, CC BY-SA 4.0, via Wikimedia Commons
Östersund: Lars Falkdalen Lindahl (User:Njaelkies Lea), CC BY-SA 3.0, via Wikimedia Commons
Bodø: Røed 20:41, 24 July 2006 (UTC), CC BY-SA 2.5, via Wikimedia Commons
Trondheim: Åge Hojem/Trondheim Havn from Trondheim, Norway, CC BY-SA 2.0, via Wikimedia Commons
Sundsvall: User:Ö1thpe0807 (image 1), User:I99limpan (image2), User:Larskallin (image3), Hans Lindqvist (image 4-5), Calle Eklund (, CC BY-SA 3.0, via Wikimedia Commons
Luleå: Andreas Harnemo, CC BY-SA 3.0, via Wikimedia Commons
Dundee: File:442 dundee header.png (Tay Bridge and RSS Discovery images):- Original: PlutosAcademy File:V&A Dundee Near Completi, CC BY-SA 4.0, via Wikimedia Commons
Glasgow: 瑞丽江的河水, CC BY-SA 4.0, via Wikimedia Commons
Ávila: Anual, CC BY 3.0, via Wikimedia Commons
Lugo: Fausto Alava-Moreno, CC BY-SA 2.0, via Wikimedia Commons
Oviedo: javier.losa, CC BY-SA 2.0, via Wikimedia Commons
Segovia: Marostegui, CC BY-SA 4.0, via Wikimedia Commons
Pau: Flo641, CC BY-SA 4.0, via Wikimedia Commons

Questions

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

Reykjavik, Iceland, at 13.2 °C cooler. Reaching it emits 741 kg CO₂e return, travelling 7h 24m each way by air (modelled).

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

Yes. Guarda reaches 5.2 °C cooler and is reachable by rail or ferry in 5h 12m (modelled), emitting 7.6 kg CO₂e return — though Reykjavik is cooler still, if you fly.

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

741 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.