Mercer Island Half – Mission/Purpose Statement

To enable participants to experience safe, well organized, and family friendly running and walking events on Mercer Island, while raising funds and awareness for both Colon Cancer prevention and for local and international Rotary endorsed charities.

Half Marathon Experience

Every year, thousands of runners and walkers cross the finish line at the annual springtime running of Mercer Island Rotary’s Half Marathon which includes 10K and 5K races along with a Kids’ Dash, all designed to help raise funds and awareness to fight colon cancer and to benefit an array of other charitable causes supported by the Foundation of the Rotary Club of Mercer Island.

While the 10K race is for runners only, both the 13.1-mile half marathon and the 5K welcome walkers as well as runners. From the starting line on the outskirts of Luther Burbank Park on the northern end of the island, the race unfolds along an out-and-back course that takes a clockwise loop around the island and features a wealth of rolling hills along the way, as well as a few uphill and downhill challenges. The race starts at an elevation of about 75 feet above sea level and dips to a low of about 30 feet in the first mile of the race, which is followed by a gradual climb over the next few miles to about 150 feet above sea level by the time runners reach the 3.5-mile point in the race, along the island’s eastern shore.

This stretch of the race is among its most winding and hilly, as runners make the gradual climb up East Mercer Way, winding left and right as the roadway curves with the shape of the land. Runners stay on East Mercer all the way down to the southern tip of the island, passing through Clarke Beach Park along the way, until East Mercer becomes West Mercer Way. There, runners begin the second half of the race that takes them northward along the western shore, where they can see Seward Park across the lake as they make their way along the winding route.

The race’s biggest hills — as well as its steepest downhill stretches — occur in the second six and a half miles of the race, as runners hit the peak point in the race by about the 9.5-mile point in the race, where the elevation reaches about 225 feet above sea level. After that, it’s mostly downhill (except for another steep hill just as runners are passing through miles 11 to 12) as the race finishes back near the park.

Race Weather & Climate

Nestled in the middle of Lake Washington between Seattle and Bellevue, Mercer Island typically experiences great race weather that can include moderately to occasionally cool weather conditions in the early spring, as well as some refreshing showers. In March/April, the island’s average monthly temperatures range between 46.2∞F and 50.2∞F and average highs range between 53.2∞F and 58.2∞F.  Monthly precipitation averages between 2.77 and 3.51 inches.