Cardiff Half Marathon

This edition is listed as Half Marathon in Cardiff, Wales, UK.

Typical race-morning air at Cardiff Half Marathon averages 13°C across the last 10 years (about 10°C to 16°C in that window). The morning can still warm as you run. The stickiest morning in that set was 2018, WBGT around 14°C. 2025 was the windiest, around 29 km/h. Use that range for planning, not as a promise for race day.

2018 (7 Oct 2018) was the hottest Cardiff Half Marathon morning in that set, WBGT around 14°C. Treat that year as the spike, not as the usual morning.

2025 (5 Oct 2025) was the windiest Cardiff Half Marathon morning in that set, around 29 km/h. Wind still changes what the same pace costs. Treat that year as the spike, not as the usual morning.

Inside about 14 days, use the live forecast on this page. The current outlook is about 13°C to 15°C, around 15 km/h wind and 67% humidity. Forecasts move. Further out, use race morning history, not a locked plan.

Heat, humidity, wind or a lumpier day than you hoped all raise the chance of a late fade. If the start feels easy, don't spend it. Back off early, and hold even effort even if that means slower than the A-goal. The preview on this page is the starting point. Full personalised splits sit in Race Pass or Pro.

About 74 m of climbing and 70 m of descent. Mostly flat. Almost all of it sits within 2%. No steep grades over 6%. Two climbs.

It is an estimate of how the course and conditions could move your baseline. Your body still decides the rest: heat adaptation, fuelling, prep, mindset, how you race, and whether you can draft.

The free page covers conditions, course context and a finish preview. Full personalised pacing and weather-adjusted splits sit in Race Pass or Pro.