Cardiff · September · relief from the heat

Coolest places to go from Cardiff in September

In September, the coolest well-known place within 15 hours of Cardiff is Reykjavik, Iceland, 7.8 °C cooler than Cardiff and 6.3 h sun a day, about 5h 54m each way by air. Without flying, it is Dundee, United Kingdom, 2.9 °C cooler than Cardiff, about 9h 30m each way by train, for about 10× less carbon (44.6 kg CO₂e return against 447 kg).

The 10 coolest places within 15 hours of Cardiff

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, Iceland7.8 °C cooler · 6.3 h sun a day · 3.5 mm rain a day · sea 10.8 °Cair ≈ 5h 54m · 447 kg CO₂e return
Tromsø, Norway5.6 °C cooler · 4.9 h sun a day · 5.2 mm rain a dayair ≈ 6h 36m · 585 kg CO₂e return
Östersund, Sweden4.6 °C cooler · 7.7 h sun a day · 2.6 mm rain a dayair ≈ 5h 42m · 421 kg CO₂e return
Bodø, Norway4.4 °C cooler · 5.2 h sun a day · 6.6 mm rain a day · sea 13.0 °Cair ≈ 6h 12m · 504 kg CO₂e return
Rovaniemi, Finland4.1 °C cooler · 6.0 h sun a day · 3.5 mm rain a dayair ≈ 6h 36m · 581 kg CO₂e return
Trondheim, Norway3.5 °C cooler · 7.0 h sun a day · 5.8 mm rain a dayair ≈ 5h 36m · 390 kg CO₂e return
Sundsvall, Sweden3.0 °C cooler · 8.4 h sun a day · 2.3 mm rain a day · sea 14.2 °Cair ≈ 5h 48m · 433 kg CO₂e return
Luleå, Sweden3.0 °C cooler · 7.7 h sun a day · 2.4 mm rain a day · sea 14.3 °Cair ≈ 6h 18m · 534 kg CO₂e return
Dundee, United Kingdom2.9 °C cooler · 7.7 h sun a day · 2.0 mm rain a day · sea 13.9 °Crail ≈ 9h 30m · 44.6 kg CO₂e return
Glasgow, United Kingdom2.3 °C cooler · 7.2 h sun a day · 3.4 mm rain a dayrail ≈ 8h 36m · 39.6 kg CO₂e return

Without flying

The coolest places the train reaches within 15 hours. Dundee is 2.9 °C cooler for 44.6 kg — about 10× less carbon than flying to Reykjavik.

Dundee, United Kingdom2.9 °C cooler · 7.7 h sun a day · 2.0 mm rain a day · sea 13.9 °Crail ≈ 9h 30m · 44.6 kg CO₂e return
Inverness, United Kingdom2.8 °C cooler · 7.3 h sun a day · 2.9 mm rain a dayrail ≈ 11h 12m · 53.9 kg CO₂e return
Aberdeen, United Kingdom2.5 °C cooler · 8.4 h sun a day · 1.6 mm rain a day · sea 13.4 °Crail ≈ 10h 42m · 50.9 kg CO₂e return
Glasgow, United Kingdom2.3 °C cooler · 7.2 h sun a day · 3.4 mm rain a dayrail ≈ 8h 36m · 39.6 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 Cardiff in September within 15 hours is Reykjavik, 7.8 °C cooler, costing 447 kg CO₂e return. The lowest-carbon option is Buxton at 17.3 kg — 26× less carbon, for 5.3 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 Cardiff. Pick one to compare.

By rail or ferry By air

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

September from Cardiff — 4 destinations on the frontier, 1 without flying.
Destination	How	CO₂e return	Temp	Sun/day	Rain/day	Journey
Buxton, United Kingdom	Rail	17.3 kg	12.8 °C	7.1 h	3.9 mm	4h 36m
Lillehammer, Norway	Air	341 kg	12.0 °C	7.0 h	4.6 mm	5h 18m
Östersund, Sweden	Air	421 kg	10.7 °C	7.7 h	2.6 mm	5h 42m
Reykjavik, Iceland	Air	447 kg	7.5 °C	6.3 h	3.5 mm	5h 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 Buxton (17.3 kg, 2.5 °C cooler) to Lillehammer (341 kg, 3.3 °C cooler) buys 0.8 °C more relief from the heat for an extra 324 kg — 405 kg of CO₂e per degree. That single step is the most expensive relief from the heat on the whole curve.

The pick of them

BuxtonUnited Kingdom17.3 kg CO₂e return12.8 °C · 7.1 h sun · 4h 36m by railmild and bright

ReykjavikIceland447 kg CO₂e return7.5 °C · 6.3 h sun · 5h 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 Cardiff

September from elsewhere

Photo credits

Buxton: Andrew Hill, CC BY-SA 2.0, 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
Aberdeen: Ragazzi00, CC BY-SA 3.0, via Wikimedia Commons

Questions

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

Reykjavik, Iceland, at 7.8 °C cooler. Reaching it emits 447 kg CO₂e return, travelling 5h 54m each way by air (modelled).

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

Yes. Buxton reaches 2.5 °C cooler and is reachable by rail or ferry in 4h 36m (modelled), emitting 17.3 kg CO₂e return — though Reykjavik is cooler still, if you fly.

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

447 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.