What is the typical weather for Ironman Wisconsin?

Ironman Wisconsin is usually held around September. Madison can bring ideal early-fall racing or a day shaped by wind, rain and temperature swings.

How should athletes check Ironman Wisconsin race-day weather?

Use the race-day planner when the forecast window opens, then check official event and local safety guidance before final decisions.

Madison, Wisconsin

Ironman Wisconsin weather

Madison can bring ideal early-fall racing or a day shaped by wind, rain and temperature swings.

IronmanSeptemberInland-water swim

Typical race window

September weather in Madison, Wisconsin

Monthly climate normal from 2016-2025 archive data.

September

Air temperature

14°C-23°C

Average wind

18 km/h

Peak daily wind

34 km/h

Wet-day chance

31%

A typical day in September averages 3.1 mm of precipitation, with average gusts around 37 km/h. Treat this as planning context, not a live forecast.

Jan

-2°C

Feb

0°C

Mar

7°C

Apr

13°C

May

20°C

Jun

26°C

Jul

28°C

Aug

26°C

Sep

23°C

Oct

15°C

Nov

7°C

Dec

1°C

Swim

Lake Monona can be affected by chop and water-quality guidance after weather changes.

Bike

Rolling terrain and exposed farm roads make wind and wet pavement meaningful.

Run

The run often benefits from moderate temperatures, unless humidity or rain lingers.

Live race-day forecast

Build the exact read when your date matters.

This race page stays evergreen. For date, start time and expected segment durations, open the race-day planner with Madison, Wisconsin prefilled.

Build your race-day read Browse races

Madison, Wisconsin

Ironman Wisconsin weather

Madison can bring ideal early-fall racing or a day shaped by wind, rain and temperature swings.

IronmanSeptemberInland-water swim

Typical race window

September weather in Madison, Wisconsin

Monthly climate normal from 2016-2025 archive data.

September

Air temperature

14°C-23°C

Average wind

18 km/h

Peak daily wind

34 km/h

Wet-day chance

31%

A typical day in September averages 3.1 mm of precipitation, with average gusts around 37 km/h. Treat this as planning context, not a live forecast.

Jan

-2°C

Feb

0°C

Mar

7°C

Apr

13°C

May

20°C

Jun

26°C

Jul

28°C

Aug

26°C

Sep

23°C

Oct

15°C

Nov

7°C

Dec

1°C

Swim

Lake Monona can be affected by chop and water-quality guidance after weather changes.

Bike

Rolling terrain and exposed farm roads make wind and wet pavement meaningful.

Run

The run often benefits from moderate temperatures, unless humidity or rain lingers.

Live race-day forecast

Build the exact read when your date matters.

This race page stays evergreen. For date, start time and expected segment durations, open the race-day planner with Madison, Wisconsin prefilled.

Build your race-day read Browse races