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Race IntelligenceHoorn, Netherlands

IRONMAN 70.3 Westfriesland

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 June 2027
Swim
1.9 km
Bike
90 km
Run
21.1 km

Published route evidence. Final 2027 route pending. Checked 11 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 Westfriesland actually gives you

You start in Hoorn’s old harbour, ride the exposed roads of Westfriesland, then run repeated passes through the historic city centre and waterfront. It looks fast. The question is whether you can use that speed without letting the harbour, the wind or the crowd choose your effort.

Show distances in

Swim

1.9 km

Lake / Open Water

Layout
1 loop
Setting
Hoorn's old harbour

Open-water conversion and a busy old-harbour start matter more than pool CSS alone.

Source: current course description

Bike

90 km

Flat Countryside

Layout
1 loop
Setting
Westfriesland's open roads
Elevation
50 m published profile difference

A flat course reduces climbing cost, while high wind exposure makes aerodynamics and pacing more important.

Source: 2025 published profile

Run

21.1 km

Flat City and Waterfront

Layout
2.5 loops
Setting
Hoorn's historic centre and Stadstrand
Elevation
40 m published profile difference

Low elevation favours rhythm; repeated city-centre turns and crowd energy can disturb it.

Source: 2024 published profile
Where these course facts come from

The swim description is from the organiser’s current course page. The elevation figures are from the latest official profiles available here: 2025 for the bike and 2024 for the run. They describe the character of the course. They do not confirm the final 2027 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

Find your water

  1. 0–300 m

    The start

    Leave the harbour without a fight

    The old-harbour start will feel busy. Your first win is finding clear water and a rhythm you can keep, not proving how fast you can sprint off the line.

    • Sight, then settle
    • Let the pack split before you spend energy

    A frantic first 300 m is not free speed

Bike

Let the wind move the speed, not the effort

  1. 0 km–15 km

    Leave Hoorn

    Get organised before the road opens

    The course carries you away from Hoorn and towards the exposed countryside. Use the change of setting to settle your breathing, get into position, and begin fuelling before speed becomes persuasive.

    • Start drinking before the open roads
    • Check effort before average speed

  2. 15 km–70 km

    Use the road

    Let the countryside set the rhythm

    On a flat, exposed bike, the wind can make a good ride look slow or a bad ride look fast. Keep the pressure even and let the road give you speed when it wants to.

    • Ride the effort, not the number
    • Use sheltered stretches to reset your position

    Do not repay a headwind by digging a hole

  3. 70 km–90 km

    Return to Hoorn

    Bring a run back into town

    As the course turns back towards Hollandia Park, stop asking the bike for proof. Finish your planned bottle, loosen the legs, and arrive ready for a run that changes direction and atmosphere more often than the bike did.

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

Run

Run your pace, not the crowd’s

  1. 0 km–7 km

    Leave Hollandia Park

    Find your feet before the city finds your pace

    The first pass from T2 towards Hoorn will feel busier and faster than your legs really are. Use the waterfront and first aid station to turn bike legs into running legs before committing to pace.

    • Shorten your stride
    • Take the first aid station deliberately

  2. 7 km–16 km

    Use the 2.5 loops

    Make repetition work for you

    The historic centre, docks and repeated landmarks give you regular feedback. Use each pass to check posture, fuelling and effort; do not let a louder part of town become a faster kilometre by accident.

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

  3. 16 km–21.1 km

    Decide

    Earn the last move

    Only here do you need to decide whether the day has given you permission to race. If it has, change one thing at a time: cadence, posture, then pace.

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

The point of the bike leg is to arrive at T2 in a condition to run, not to arrive with the fastest split the legs could physically produce.

Ironman 70.3 Race Strategy: Pace to Run Well

04 Race week

What I would keep an eye on

There is no useful 2027 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
15.0–24.2°CDew point centred on 13.4°C
Wind and gusts
13.9 km/hGusts up to 42.8 km/hPrevailing direction 216°
Rain likelihood
Up to 75%Wet-surface uncertainty retained

Historical baseline, 2019–2025 · Open-Meteo historical archive · Updated 2026-09-11.Historical comparison only. This is not a forecast for 2027.

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 2027 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 standard 70.3 distances 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 Westfriesland 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 carries you back into Hoorn's noise and landmarks.

Evidence

Sources and verification

Course status: Partially verified. The organiser’s descriptions and latest published route profiles are in use. The final 2027 route is not yet confirmed. Last checked 2026-09-11.