Ironman 70.3 Coeur d'Alene promises to be challenging, but weather could make things even more interesting — and raise the difficulty level.

According to the National Weather Service, it should be mostly cloudy with a 40% chance of rain showers. Highs are projected to be in the 60s and perhaps top 70.

The rain could make for slick road conditions as cyclists head to Higgens Point, then south on U.S. for about 20 miles before turning back.

Winds are projected to be fairly mild in the morning, about 2-3 mph, which could provide a calm Lake Coeur d'Alene for swimmers who will start their day at 6 a.m. If forecasts hold, swimmers should be out of the water before stronger winds create choppy conditions.

Last year's swim for Ironman 70.3 Coeur d'Alene was shortened to 500 meters from 1.2 miles due to rough waters. Ironman has said decisions to shorten or even cancel a swim are made “in the interest of athlete safety.” 

One Ironman athlete recalled the Ironman Coeur d'Alene in 2007 was particularly rough, but wasn't canceled or shortened.

"The water was so rough that they made the swim optional. Athletes were allowed to skip the swim, would still get a finisher's medal, but could not (obviously) use the time for any qualifying races," they wrote.

Lake Coeur d'Alene has warmed up well and should be about 63 degrees Sunday.

The race has more than 100 locals, including about 75 from Coeur d'Alene and about 25 each from Post Falls and Hayden.

The youngest locals include 18-year-old Madison Price and 19-year-old Lia Ramey, while the oldest are 71-year-old Lee Plourde and 68-year-old David Barnett.