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Race IntelligenceWeymouth, United Kingdom

IRONMAN 70.3 Weymouth

Know your day before you race it.

Enter four numbers you already train with. You get a likely finish range, target paces and watts, and how I would race this course.

Race day
20 September 2026
Swim
1.9 km
Bike
90 km
Run
21.1 km

Published route evidence. Final 2026 route pending. Checked 13 Sept 2026.

Official course routeThe real GPS route for each discipline with official GPX data available, drawn in one shared coordinate space.

01 Race Card

Build my Race Card

Your first range uses conservative assumptions. Add optional evidence to make it more specific. It is calculated in your browser and saved only on this device.

Your numbers
Distance unit
Weight unit
You and this race
Sharpen your range with more detailOptional. Recent swim, bike and run results, equipment and transitions.

Add only the evidence you have. Every control changes a discipline range, its uncertainty, or an execution-risk explanation.

Swim evidence

Replaces the broad pool-to-open-water assumption.

Bike and equipment

These replace broad mass, aerodynamics, tyre, and power-to-speed assumptions.

Run evidence

A recent effort and honest durability/acclimation answers refine the post-bike run.

Race execution

Transition proficiency changes the T1/T2 range and how wet conditions are treated.

02 The course

What Weymouth actually gives you

You swim a calm, sheltered triangle in Weymouth Bay, then take on a single 90 km loop through the rolling Dorset countryside before returning to a flat, fully exposed run along the town's seafront. The bike is the leg with real terrain to respect. The run then asks a simple question: did you pace the hills well enough to still move well along the esplanade.

Show distances in

Swim

1.9 km

Bay / Open Water

Layout
1 loop, triangle
Setting
Weymouth Bay, off the town beach

A naturally sheltered bay and a self-seeded rolling start remove most of the pace penalty a rougher, mass-start open-water swim would add.

Source: 2026 course description

Bike

90 km

Rolling Countryside

Layout
1 loop
Setting
Dorset countryside via Dorchester, Godmanstone and King's Stag
Elevation
800 m published profile difference

800 m of rolling elevation over one 90 km loop is real climbing cost the model needs to respect, unlike a flat course.

Source: 2026 published profile

Run

21.1 km

Flat Coastal Esplanade

Layout
2.5 loops
Setting
Weymouth's seafront Esplanade and town centre
Elevation
50 m published profile difference

A flat, fully exposed seafront course rewards even pacing; there is no shelter from wind or sun and no terrain to hide a bad decision behind.

Source: 2026 published profile
Where these course facts come from

These facts come from the organiser’s latest published material: swim, 2026 course description; bike, 2026 published profile; run, 2026 published profile. They describe the character of the course. They do not confirm the final 2026 route.

03 Race plan

How I’d want you to race it

One job for each part of this course. The distance markers tell you when the job changes. The course tells you why.

Swim

Settle into the triangle

  1. 0–300 m

    The start

    Use the rolling start, don't waste it

    A self-seeded rolling start means you are not fighting for space the way a mass start forces you to. Enter smoothly, find the first buoy line, and settle into the triangle shape before you commit to a pace.

    • Seed honestly
    • Settle before you commit to pace

    A calm start is not permission to sprint the first 300 m

Bike

Respect the hills, then let the flat give it back

  1. 0 km–16 km

    Leave Weymouth

    Get organised before the hills start

    The course heads inland from the coast towards Dorchester. Use these first kilometres to settle your breathing, get into position, and start fuelling before the rolling terrain asks anything of you.

    • Start drinking before the climbing begins
    • Check effort before speed

  2. 16 km–64 km

    The Dorset loop

    Ride the hills by effort, not by feel

    This is where the course's 800 m of climbing sits, out through Godmanstone towards King's Stag and back. A short climb ridden too hard here costs you more on the run than it ever gains on the clock.

    • Shift early, spin the climbs
    • Use the descents to recover, not to attack

    Chasing a strong rider up a hill is not a pacing plan

  3. 64 km–90 km

    Return to Weymouth

    Bring a run back into town

    As the course flattens back towards the coast through Broadmayne and Preston, stop asking the legs for proof. Finish your planned nutrition, loosen your cadence, and arrive at T2 ready to run.

    • Finish the bottle you planned
    • Let cadence rise before T2

Run

Hold the esplanade pace

  1. 0 km–7 km

    Find your legs

    The esplanade will feel faster than it is

    The first out-and-back towards Overcombe is flat, open and fast-looking. Use it to turn bike legs into running legs rather than committing to a pace the climbing you just did hasn't earned yet.

    • Shorten your stride out of T2
    • Take the first aid station deliberately

  2. 7 km–16 km

    Use the repeats

    Let the laps check you, not excite you

    The course repeats the same seafront out-and-back with a short loop past the finish each time. Use each pass as a checkpoint for posture, fuelling and effort rather than letting the crowd near the finish pull your pace early.

    • Assign a check to each landmark
    • Keep fuelling before you feel empty

    The finish line you pass twice is not your finish line

  3. 16 km–21.1 km

    Decide

    Earn the last move

    Only on the final partial lap should you decide whether the day has given you permission to race. If it has, change one thing at a time: cadence, then posture, then pace.

    • Look for three good kilometres
    • Keep the finish decision yours

04 Race week

What I would keep an eye on

There is no useful 2026 forecast this far out. For now, past race dates give us a point of reference. Closer to the race, the forecast will tell us whether the plan needs changing.

Forecast statusToo early for a forecast

A race-day forecast is not meaningful yet; check back closer to the event.

Temperature
11.3–19.0°CDew point centred on 11.9°C
Wind and gusts
16.7 km/hGusts up to 58.7 km/hPrevailing direction 310°
Rain likelihood
Up to 85%Wet-surface uncertainty retained

Historical baseline, 2019–2025 · Open-Meteo historical archive · Updated 2026-09-13.Historical comparison only. This is not a forecast for 2026.

05 Method

What goes into your range

Your CSS, FTP, weight and run threshold create the first range. Open-water, bike, run and execution evidence can replace broad assumptions. Course data and the historical conditions baseline shape every simulation.

  1. Your numbersCSS · FTP · weight · run threshold
  2. This raceDistance · water type · elevation · exposure
  3. Your Race CardFinish and discipline ranges, with target paces and watts

Confidence is built from four inputs

Athlete evidence
Builds with recent open-water, bike and run efforts
Bike setup
Builds with equipment, mass, aero and tyre detail
Course evidence
Partial while the 2026 route is unconfirmed
Race-week conditions
Historical baseline until a forecast is useful
How the model works

It starts with the targets in your Race Card, then samples the parts of a 70.3 that vary: open-water pace, transitions, bike speed at the planned power, and the drop in run performance after the swim and bike. Repeating that calculation produces a likely range rather than a single heroic number.

The current time calculation uses this race’s published distances, or standard 70.3 distances where none are published, with the available course headings, elevation and exposure evidence. Weather scenarios vary temperature, dew point, wind, gusts, rain and water conditions together. Unknown route detail stays visible as uncertainty rather than false precision.

It is not predicting your exact finishing time, placing, or race-day weather. It answers a narrower question: given the plan and the information we have, what range of day is plausible, and where is the uncertainty coming from?

Confidence is not a permanent “low”. It is recalculated across four separate inputs:

  • Your evidence: consistent inputs and recent race-like swim, bike, and run results.
  • Bike setup: measured or specified aerodynamics rather than a broad prior.
  • The course: verified distance and route character, including elevation and technical sections.
  • The conditions: a current forecast is more useful than a historical comparison.

It starts low when those inputs are broad. It can become moderate or high as the evidence improves. A narrower range means better information, not a guarantee.

06 Next steps

If Weymouth is your race

Your range is built on today’s numbers. The months of training before race day decide what those numbers become.

The work from here.

Self-guided routeHalf-distance training plansTraining plans for the fitness and durability this course asks for.See the plans Personalised routeWork with me on the whole buildCoaching when you want the plan, feedback and race decisions joined up.See coaching

Further reading

ArticleHow to pace a 70.3 so you can still runThe longer version of the swim-bike-run pacing logic behind this Race Card.ArticleFix the first ten minutes off the bikeUseful before a run that immediately asks you to turn climbing legs into running legs.

Evidence

Sources and verification

Course status: Partially verified. The organiser’s descriptions and latest published route profiles are in use. The final 2026 route is not yet confirmed. Last checked 2026-09-13.